Showing posts with label Velocity. Show all posts
Showing posts with label Velocity. Show all posts

Monday, June 22, 2026

NCERT Solutions Class 11 Physics Chapter 2 Exercise 2.15 to 2.18 with Answers

 - Dr.Sanjaykumar Pawar  




```html NCERT Class 11 Physics Chapter 2 Exercise 2.15 to 2.18 Solutions

NCERT Solutions

Class 11 Physics

Chapter 2: Motion in a Straight Line

Exercise 2.15 to 2.18

Question 2.15

Suggest a suitable physical situation for each of the following graphs (Fig. 2.12).

(a) Position-Time Graph (x–t)

Observation:

  • The particle remains at rest initially.
  • Then moves away from the origin with constant velocity.
  • Returns towards the origin with constant velocity.
  • Finally comes to rest again.

Suitable Physical Situation:

A person standing on a straight road starts walking uniformly away from the origin, reaches a point A, turns back, crosses the origin at B and finally stops at another point.

The graph represents a person moving away from the origin, returning back and finally coming to rest.

(b) Velocity-Time Graph (v–t)

Observation:

  • Velocity decreases linearly.
  • Changes sign repeatedly.
  • Magnitude decreases after every interval.

Suitable Physical Situation:

A ball thrown vertically upward repeatedly strikes the ground and rebounds. Each collision reduces its speed due to loss of energy.

The graph represents the motion of a bouncing ball with decreasing speed after each rebound.

(c) Acceleration-Time Graph (a–t)

Observation:

  • Acceleration is zero for most of the time.
  • A sudden positive acceleration occurs for a short interval.

Suitable Physical Situation:

A vehicle moving uniformly receives a sudden push or the accelerator is pressed for a short duration.

The graph represents a body receiving acceleration for a short time and then moving uniformly again.

Question 2.16

Figure 2.13 gives the x–t plot of a particle executing one-dimensional simple harmonic motion. Give the signs of position (x), velocity (v) and acceleration (a) at: (i) t = 0.3 s (ii) t = 1.2 s (iii) t = –1.2 s

Principle Used:

Acceleration in SHM: a = -ω²x Velocity is given by the slope of the x-t graph.

(i) At t = 0.3 s

  • x is negative.
  • Slope is negative.
  • Acceleration is positive.
x < 0, v < 0, a > 0

(ii) At t = 1.2 s

  • x is positive.
  • Slope is positive.
  • Acceleration is negative.
x > 0, v > 0, a < 0

(iii) At t = –1.2 s

  • x is positive.
  • Slope is positive.
  • Acceleration is negative.
x > 0, v > 0, a < 0
Time Position (x) Velocity (v) Acceleration (a)
0.3 s Negative Negative Positive
1.2 s Positive Positive Negative
–1.2 s Positive Positive Negative

Question 2.17

Figure 2.14 gives the x–t plot of a particle in one-dimensional motion. Three different equal intervals of time are shown. In which interval is the average speed greatest and in which is it least? Give the sign of average velocity for each interval.

Concept:

Average Velocity = Change in Position / Time Average Speed = Distance Travelled / Time

Since all intervals have equal duration, the interval with the greatest change in position will have the greatest average speed.

Interval 1

  • Position increases slowly.
  • Average velocity is positive.

Interval 2

  • Position increases rapidly.
  • Average velocity is positive.

Interval 3

  • Position decreases rapidly.
  • Average velocity is negative.
Greatest Average Speed = Interval 3

Least Average Speed = Interval 1
Interval Sign of Average Velocity
1 Positive
2 Positive
3 Negative

Question 2.18

Figure 2.15 gives a speed-time graph of a particle moving in a constant direction. Three equal intervals of time are shown. (a) In which interval is the average acceleration greatest in magnitude? (b) In which interval is the average speed greatest? (c) Choosing the positive direction as direction of motion, give signs of velocity and acceleration in the three intervals. (d) What are the accelerations at points A, B, C and D?

(a) Average Acceleration

Average Acceleration = Change in Speed / Time

Since all intervals have equal duration, the third interval shows the largest change in speed.

Greatest Average Acceleration occurs in Interval 3.

(b) Average Speed

The average speed is greatest in the interval where the speed values are highest.

Average Speed is greatest in Interval 3.

(c) Signs of Velocity and Acceleration

Interval Velocity Acceleration
1 Positive Positive
2 Positive Negative
3 Positive Positive

(d) Accelerations at A, B, C and D

Acceleration is equal to the slope of the speed-time graph.

At A → Positive slope → aA > 0 At B → Slope = 0 → aB = 0 At C → Slope = 0 → aC = 0 At D → Slope = 0 → aD = 0
aA > 0, aB = 0, aC = 0, aD = 0
```

Educational diagram illustrating NCERT Class 11 Physics Motion in a Straight Line solutions including position-time, velocity-time, acceleration-time graphs and SHM analysis.
NCERT Class 11 Physics Chapter 2 Motion in a Straight Line Exercise 2.15 to 2.18 solved with graphs, SHM concepts, velocity and acceleration analysis. 



Internal Links
Class 11 Physics Motion in a Straight Line Notes
Instantaneous Velocity and Acceleration Notes
NCERT Physics Chapter 2 Important Questions
Numerical Problems on Motion in a Straight Line
Kinematics MCQs for NEET and JEE
Previous Year Questions on Motion in One Dimension
Difference Between Speed and Velocity
Graphs in Physics Explained
Simple Harmonic Motion Basics
Class 11 Physics Revision Notes
NCERT Solutions Chapter 2 Complete Series
Physics Formula Sheet for Class 11
NEET Physics Kinematics Practice Questions
JEE Motion in a Straight Line Problems
CBSE Class 11 Physics Sample Questions

NCERT Class 11 Physics Chapter 2 Exercise 2.8 to 2.14 Solutions (CBSE 2026)

-  Dr.Sanjaykumar Pawar  

 


Internal Links

  1. NCERT Class 11 Physics Chapter 2 Motion in a Straight Line Notes

  2. NCERT Class 11 Physics Exercise 2.1 to 2.7 Solutions

  3. NCERT Class 11 Physics Chapter 3 Motion in a Plane Solutions

  4. Important Class 11 Physics Formulas PDF

  5. CBSE Class 11 Physics Previous Year Questions

  6. Motion in a Straight Line MCQs with Answers

  7. Speed, Velocity and Acceleration Notes

  8. Class 11 Physics Revision Notes

  9. NCERT Exemplar Class 11 Physics Solutions

  10. Complete Class 11 Physics Study Material

```html NCERT Class 11 Physics - Motion in a Straight Line - Exercise 2.8 to 2.14 Solutions

NCERT Solutions Class 11 Physics

Chapter 2: Motion in a Straight Line

Exercise 2.8 to 2.14

Question 2.8

A ball is dropped from a height of 90 m on a floor. At each collision with the floor, the ball loses one tenth of its speed. Plot the speed-time graph of its motion between t = 0 to 12 s.

Given:

  • Height = 90 m
  • g = 9.8 m/s²
  • Loss of speed after every collision = 10%

Step 1: Time taken to reach the floor

h = ½gt²

90 = ½ × 9.8 × t²

t² = 180/9.8

t = 4.29 s

Step 2: Speed just before collision

v = gt

v = 9.8 × 4.29

v = 42 m/s

Step 3: Speed after collision

v' = 0.9 × 42

v' = 37.8 m/s

Step 4: Time taken to move upward

t = v'/g

t = 37.8/9.8

t = 3.86 s

Graph Description:

  • Speed increases uniformly from 0 to 42 m/s during first 4.29 s.
  • At collision speed suddenly decreases to 37.8 m/s.
  • Speed decreases linearly to zero while moving upward.
  • Then increases again while falling downward.
Speed-Time graph consists of straight line segments with sudden vertical drops at collisions.

Question 2.9

Explain clearly, with examples, the distinction between: (a) Magnitude of displacement and total path length (b) Magnitude of average velocity and average speed.

(a) Magnitude of Displacement and Total Path Length

Magnitude of Displacement Total Path Length
Shortest distance between initial and final positions. Actual distance travelled.
Depends only on initial and final positions. Depends on actual path followed.
Always less than or equal to path length. Always greater than or equal to displacement.

Example:

Particle moves 3 m east and 4 m north. Displacement = √(3² + 4²) = 5 m Path Length = 3 + 4 = 7 m

(b) Magnitude of Average Velocity and Average Speed

Average Velocity = Displacement / Time
Average Speed = Total Path Length / Time

Since total path length ≥ displacement,

Average Speed ≥ Magnitude of Average Velocity
Equality occurs only when motion is along a straight line without changing direction.

Question 2.10

A man walks on a straight road from his home to a market 2.5 km away with a speed of 5 km h⁻¹. Finding the market closed, he instantly turns and walks back home with a speed of 7.5 km h⁻¹. Find: (a) Magnitude of average velocity (b) Average speed

(a) Magnitude of Average Velocity

Net displacement = 0 Average Velocity = 0 / Total Time = 0
Magnitude of Average Velocity = 0 km h⁻¹

(b) Average Speed

Time to market = 2.5/5 = 0.5 h
Time to return = 2.5/7.5 = 0.333 h
Total distance = 5 km Total time = 0.5 + 0.333 = 0.833 h
Average Speed = 5 / 0.833 = 6 km h⁻¹
Average Speed = 6 km h⁻¹

Question 2.11

Why is there no distinction between instantaneous speed and magnitude of instantaneous velocity?

Instantaneous Speed = Magnitude of Instantaneous Velocity

Velocity has both magnitude and direction, whereas speed is only magnitude. At any instant, speed is simply the magnitude of velocity.

Instantaneous Speed = |Instantaneous Velocity|

Question 2.12

Look at the graphs (a) to (d) carefully and state which of these cannot represent one-dimensional motion of a particle.

  • Graph (a): Impossible because one instant corresponds to more than one position.
  • Graph (b): Impossible because one instant corresponds to more than one velocity.
  • Graph (c): Impossible because speed cannot be negative.
  • Graph (d): Impossible because total path length can never decrease.
All graphs (a), (b), (c) and (d) cannot represent one-dimensional motion.

Question 2.13

Figure 2.11 shows the x-t plot of one-dimensional motion of a particle. Is it correct to say from the graph that the particle moves in a straight line for t < 0 and on a parabolic path for t > 0?

No. The graph is an x-t graph and not the actual trajectory of the particle.

For t < 0, x remains constant, showing that the particle is at rest.

For t > 0, x increases with time and velocity increases continuously.

The graph represents variation of position with time and not the actual path of motion.

Question 2.14

A policeman moving at 30 km h⁻¹ fires a bullet at a thief's car speeding away in the same direction with a speed of 192 km h⁻¹. If the muzzle speed of the bullet is 150 m s⁻¹, with what speed does the bullet hit the thief's car?

Step 1: Convert speeds into m/s

Policeman = 30 × 5/18 = 8.33 m/s
Thief = 192 × 5/18 = 53.33 m/s

Step 2: Bullet speed relative to ground

Bullet speed = 150 + 8.33 = 158.33 m/s

Step 3: Relative speed of bullet with respect to thief

158.33 − 53.33 = 105 m/s
Speed of bullet relative to thief's car = 105 m/s
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Sunday, June 21, 2026

Kinematics Equations Explained for NEET | 3 Equations of Motion Notes

Kinematics Equations – Easy NEET Notes

KINEMATICS EQUATIONS – EASY NEET NOTES

1. Three Important Equations of Motion

These equations are used for:

  • ✅ Straight line motion
  • ✅ Constant acceleration

They connect:

  • Initial velocity (\(v_0\))
  • Final velocity (\(v\))
  • Acceleration (\(a\))
  • Time (\(t\))
  • Displacement (\(x\))

First Equation of Motion

\[ v = v_0 + at \]

Meaning

Final velocity = Initial velocity + increase in velocity due to acceleration.

Use

  • Time is given
  • Need to find velocity

Second Equation of Motion

\[ x = v_0 t + \frac12 at^2 \]

Meaning

Displacement depends on:

  • Initial velocity
  • Time
  • Acceleration
Important Point:
The term \(at^2\) shows the effect of acceleration.

Third Equation of Motion

\[ v^2 = v_0^2 + 2ax \]
Important Feature:
This equation has NO time term.

Use

  • Time is not given
  • Need relation between velocity and displacement

2. General Form of Equations

Earlier we assumed:

\[ x_0 = 0 \]

Meaning particle starts from origin.

If particle starts from another position (\(x_0\)), equations become:

Modified Second Equation

\[ x = x_0 + v_0 t + \frac12 at^2 \]

Meaning

Final position =

  • Initial position
  • Displacement due to initial velocity
  • Displacement due to acceleration

Modified Third Equation

\[ v^2 = v_0^2 + 2a(x-x_0) \]
Important Concept:
\((x-x_0)\) represents displacement.

3. Derivation Using Calculus

Definition of Acceleration

Acceleration is rate of change of velocity.

\[ a=\frac{dv}{dt} \]

Rearranging:

\[ dv = a\,dt \]

Integrating Both Sides

\[ \int_{v_0}^{v} dv = \int_0^t a\,dt \]

Since acceleration is constant:

\[ v-v_0 = at \]

Therefore:

\[ v=v_0+at \]

This gives first equation of motion.

4. Derivation of Second Equation

Velocity:

\[ v=\frac{dx}{dt} \]

So,

\[ dx=v\,dt \]

Substitute:

\[ v=v_0+at \]

Then,

\[ dx=(v_0+at)dt \]

Integrating:

\[ x-x_0=v_0 t+\frac12 at^2 \]

Hence,

\[ x=x_0+v_0 t+\frac12 at^2 \]

5. Derivation of Third Equation

We write:

\[ a=\frac{dv}{dt} \]

Using chain rule:

\[ a=\frac{dv}{dx}\frac{dx}{dt} \]

But,

\[ \frac{dx}{dt}=v \]

So,

\[ a=v\frac{dv}{dx} \]

Rearranging:

\[ v\,dv=a\,dx \]

Integrating both sides:

\[ \int_{v_0}^{v} v\,dv = \int_{x_0}^{x} a\,dx \]

After integration:

\[ \frac{v^2-v_0^2}{2}=a(x-x_0) \]

Finally:

\[ v^2=v_0^2+2a(x-x_0) \]

6. Advantage of Calculus Method

✅ This method can also be used for non-uniform acceleration.

Normal equations work only for constant acceleration.

7. Example 2.3 – Ball Thrown Vertically Upward

Given

  • Initial velocity: \(v_0=20\,m/s\)
  • Acceleration due to gravity: \(a=-10\,m/s^2\)
  • At highest point: \(v=0\)

Finding Maximum Height

Using:

\[ v^2=v_0^2+2a(y-y_0) \]

Substitute values:

\[ 0=(20)^2+2(-10)(y-y_0) \]
\[ 0=400-20(y-y_0) \]
\[ 20(y-y_0)=400 \]
\[ y-y_0=20\,m \]
Answer:
Maximum height reached = 20 m

8. Important NEET Sign Convention

Upward direction positive.

  • Upward velocity → positive
  • Gravity → negative
\[ a=-g \]

9. Important NEET Concepts

At Highest Point

Velocity becomes zero temporarily.

\[ v=0 \]

But acceleration is still:

\[ a=-g \]

10. Quick Formula Revision

Formula Use
\(v=v_0+at\) Velocity-time relation
\(x=v_0t+\frac12at^2\) Displacement-time relation
\(v^2=v_0^2+2ax\) Velocity-displacement relation
\(a=\frac{dv}{dt}\) Definition of acceleration
\(v=\frac{dx}{dt}\) Definition of velocity

11. Most Important NEET Tips

✅ Use equations only for constant acceleration.

✅ Check sign convention carefully.

✅ For upward motion: \[ a=-g \]
✅ At top point: \[ v=0 \] NOT acceleration zero.

✅ Third equation is most useful when time is absent.
© Easy NEET Physics Notes – Kinematics Equations

CBSE Class 11 Physics: Kinematics Equations of Motion Questions and Answers

Multiple Choice Questions (MCQs)

Question: Which equation is known as the first equation of motion?

Answer: v = u + at

Question: Which equation of motion does not contain time?

Answer: v² = u² + 2as

Question: What is the velocity of a body at the highest point of vertical upward motion?

Answer: Zero.

Question: What is the SI unit of acceleration?

Answer: Metre per second square (m/s²).

Question: Under which condition can equations of motion be applied?

Answer: When acceleration remains constant.


Very Short Answer Questions

Question: Define acceleration.

Answer: Acceleration is the rate of change of velocity with respect to time.

Question: Write the SI unit of displacement.

Answer: Metre (m).

Question: Write the third equation of motion.

Answer: v² = u² + 2as

Question: What is the acceleration due to gravity near the Earth's surface?

Answer: Approximately 9.8 m/s² downward.

Question: What happens to velocity at the highest point of upward motion?

Answer: Velocity becomes zero momentarily.


Short Answer Questions

Question: Write all three equations of motion.

Answer:

First Equation:

v = u + at

Second Equation:

s = ut + ½at²

Third Equation:

v² = u² + 2as

Question: Why is the third equation of motion useful?

Answer: The third equation is useful when time is not given. It directly relates velocity, displacement, and acceleration.

Question: Explain the sign convention used in vertical upward motion.

Answer:

  • Upward direction is taken as positive.
  • Upward velocity is positive.
  • Acceleration due to gravity is negative.
  • Downward displacement is negative.

Question: A car starts from rest and accelerates uniformly at 2 m/s² for 5 seconds. Find its final velocity.

Answer:

Given:

Initial velocity, u = 0

Acceleration, a = 2 m/s²

Time, t = 5 s

Using v = u + at

v = 0 + (2 × 5)

v = 10 m/s

Final Velocity = 10 m/s


Long Answer Questions

Question: Derive the first equation of motion.

Answer:

Acceleration is defined as:

a = (v − u)/t

Rearranging:

at = v − u

Therefore,

v = u + at

This is called the first equation of motion.

Question: Derive the second equation of motion.

Answer:

Average velocity = (u + v)/2

Displacement:

s = (u + v)t/2

Using the first equation:

v = u + at

Substituting:

s = [u + (u + at)]t/2

s = (2u + at)t/2

s = ut + ½at²

This is the second equation of motion.

Question: A ball is thrown vertically upward with a speed of 20 m/s. Calculate the maximum height reached.

Answer:

Given:

u = 20 m/s

v = 0

a = -10 m/s²

Using:

v² = u² + 2as

0 = (20)² + 2(-10)s

0 = 400 - 20s

20s = 400

s = 20 m

Maximum height reached = 20 m


Assertion and Reason Questions

Assertion: At the highest point of upward motion, velocity becomes zero.

Reason: Acceleration due to gravity becomes zero.

Answer: Assertion is true but Reason is false.

Assertion: The third equation of motion is useful when time is absent.

Reason: It does not contain time.

Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

Assertion: Equations of motion can be used for variable acceleration.

Reason: These equations are derived assuming constant acceleration.

Answer: Assertion is false but Reason is true.


Fill in the Blanks

Question: The SI unit of velocity is ________.

Answer: m/s

Question: The acceleration due to gravity is approximately ________.

Answer: 9.8 m/s²

Question: The equation v = u + at is called the ________ equation of motion.

Answer: First

Question: At the highest point of upward motion, velocity becomes ________.

Answer: Zero

Question: The third equation of motion does not contain ________.

Answer: Time


Case Study Based Questions

A student throws a ball vertically upward with an initial velocity of 20 m/s. The ball rises upward, reaches maximum height, and then falls back to the ground. Assume g = 10 m/s².

Question: What is the velocity at the highest point?

Answer: 0 m/s

Question: What is the acceleration at the highest point?

Answer: 10 m/s² downward.

Question: Which equation can be used to find the maximum height?

Answer: v² = u² + 2as

Question: Calculate the maximum height.

Answer: 20 m


Match the Following

Column A Column B
First Equation of Motion v = u + at
Second Equation of Motion s = ut + ½at²
Third Equation of Motion v² = u² + 2as
Acceleration Rate of change of velocity

Important Numerical Problems

Question: A body starts from rest and accelerates uniformly at 4 m/s² for 5 seconds. Find the final velocity.

Answer:

v = u + at

v = 0 + (4 × 5)

v = 20 m/s

Final Velocity = 20 m/s

Question: A car moving with a velocity of 10 m/s accelerates at 2 m/s² for 5 seconds. Find the displacement.

Answer:

s = ut + ½at²

s = (10 × 5) + ½(2)(25)

s = 50 + 25

s = 75 m

Displacement = 75 m

Physics infographic showing kinematics equations, derivation of motion formulas, velocity, acceleration, displacement and NEET preparation notes.
Three equations of motion used in kinematics for constant acceleration explained with formulas and applications. 



 INTERNAL LINKS
Motion in a Straight Line Notes
Velocity and Acceleration Explained
Example 3.4 Solution Explained for Beginners
Block and Trolley System NEET Solution
Newton's Laws of Motion Notes
Vector Addition and Subtraction
Important Physics Derivations for NEET
Projectile Motion Notes
Free Fall and Gravity Problems
NCERT Kinematics Solutions

Wednesday, May 27, 2026

Acceleration Notes for Class 11 Physics CBSE & NEET

 Acceleration

├── Definition

│   ├── Rate of change of velocity

│   ├── Vector quantity

│   └── Has magnitude + direction

├── Velocity Change

│   ├── Change in speed

│   ├── Change in direction

│   └── Both speed and direction

├── Average Acceleration

│   ├── Formula

│   │   └── a = Δv / Δt

│   │

│   ├── Terms

│   │   ├── Δv = change in velocity

│   │   └── Δt = time interval

│   │

│   └── Direction

│       └── Same as Δv

├── Instantaneous Acceleration

│   ├── Acceleration at a particular instant

│   ├── Very small time interval

│   └── Formula

│       └── a = dv / dt

├── Motion in x-y Plane

│   ├── Velocity Components

│   │   ├── vx = v cosθ

│   │   └── vy = v sinθ

│   │

│   ├── Acceleration Components

│   │   ├── ax = dvx/dt

│   │   └── ay = dvy/dt

│   │

│   └── Vector Form

│       └── a = ax i + ay j

├── Graphical Understanding

│   ├── Velocity changes from point to point

│   ├── Δv found by vector subtraction

│   ├── Smaller Δt gives accurate acceleration

│   └── Δt → 0 gives instantaneous acceleration

├── Units

│   ├── SI Unit

│   │   └── m/s²

│   │

│   └── Dimensional Formula

│       └── [M⁰L¹T⁻²]

├── Special Cases

│   ├── Constant velocity

│   │   └── Acceleration = 0

│   │

│   ├── Negative acceleration

│   │   └── Retardation / Deceleration

│   │

│   └── Circular motion

│       └── Acceleration exists due to direction change

└── Important NEET Formulas

    ├── a = Δv / Δt

    ├── a = dv / dt

    ├── ax = dvx / dt

    ├── ay = dvy / dt

    ├── vx = v cosθ

    └── vy = v sinθ 



Educational diagram explaining acceleration in Class 11 Physics with velocity vectors, formulas, x-y plane motion, and acceleration components.
Class 11 Physics Acceleration Notes with
 Formulas and Vector Components for CBSE and NEET Students 


- Dr.Sanjaykumar pawar

  Acceleration Notes - NEET Level

Acceleration Notes (NEET Level)

1. What is Acceleration?

Acceleration tells us how quickly velocity changes with time.

  • If speed changes → acceleration exists.
  • If direction changes → acceleration exists.
  • If both change → acceleration exists.

Acceleration is a vector quantity because it has both magnitude and direction.


2. Average Acceleration

Average acceleration is defined as:

Average Acceleration = Change in Velocity / Time Interval
a = Δv / Δt

Where:

  • a = average acceleration
  • Δv = change in velocity
  • Δt = time interval

3. Velocity Components in x-y Plane

In two-dimensional motion, velocity has two components:

  • vx → velocity along x-axis
  • vy → velocity along y-axis
Δv = Δvx i + Δvy j

Therefore acceleration becomes:

a = (Δvx / Δt)i + (Δvy / Δt)j

Where:

  • i = unit vector along x-axis
  • j = unit vector along y-axis

4. Components of Acceleration

a = ax i + ay j

Where:

  • ax = acceleration along x-axis
  • ay = acceleration along y-axis

5. Instantaneous Acceleration

Instantaneous acceleration means acceleration at a particular instant of time.

It is obtained when the time interval becomes extremely small.

a = lim (Δt → 0) (Δv / Δt)

6. Component Form of Instantaneous Acceleration

ax = dvx / dt
ay = dvy / dt

Meaning:

  • ax = rate of change of velocity along x-axis
  • ay = rate of change of velocity along y-axis

7. Graphical Understanding of Acceleration

Suppose an object moves from point P to another point after a small time interval Δt.

  • The velocity changes from v to another value.
  • The change in velocity is called Δv.
  • The direction of acceleration is same as the direction of Δv.

As Δt becomes smaller:

  • Average acceleration approaches instantaneous acceleration.
  • The direction becomes more accurate.

8. Velocity Components

If velocity makes angle θ with x-axis:

vx = v cos θ
vy = v sin θ

Where:

  • vx = horizontal component
  • vy = vertical component

9. SI Unit of Acceleration

m/s²

Read as: metre per second square


10. Dimensional Formula

[M⁰L¹T⁻²]

11. Important NEET Points

  • Acceleration depends on change in velocity.
  • Constant velocity means acceleration is zero.
  • Negative acceleration is called retardation or deceleration.
  • In circular motion, acceleration exists even if speed is constant because direction changes continuously.

12. Formula Summary Table

Concept Formula
Average Acceleration a = Δv / Δt
Instantaneous Acceleration a = dv / dt
x-component ax = dvx / dt
y-component ay = dvy / dt
Velocity Components vx = v cos θ, vy = v sin θ

Quick Revision

  • Acceleration = Rate of change of velocity.
  • It is a vector quantity.
  • SI unit = m/s².
  • Velocity change can be due to speed or direction change.
  • Average acceleration uses finite time interval.
  • Instantaneous acceleration uses very small time interval.
Class 11 Physics - Acceleration Questions and Answers

Class 11 Physics - Acceleration Questions and Answers

1. Multiple Choice Questions (MCQs)

Q1. Acceleration is defined as:

A. Change in displacement
B. Change in speed
C. Change in velocity per unit time
D. Distance travelled per unit time

Answer: C. Change in velocity per unit time

Q2. SI unit of acceleration is:

A. m/s
B. m/s²
C. m²/s
D. km/h

Answer: B. m/s²

Q3. Which of the following is a vector quantity?

A. Distance
B. Speed
C. Time
D. Acceleration

Answer: D. Acceleration

2. Very Short Answer Questions

Q1. Define acceleration.

Answer: Acceleration is the rate of change of velocity with time.

Q2. Write the SI unit of acceleration.

Answer: m/s²

Q3. Is acceleration a scalar or vector quantity?

Answer: Vector quantity.

3. Short Answer Questions

Q1. Differentiate between average acceleration and instantaneous acceleration.

Average Acceleration Instantaneous Acceleration
Calculated over a finite time interval Calculated at a particular instant
a = Δv / Δt a = dv / dt
Gives average change Gives exact change

Q2. Why is acceleration a vector quantity?

Answer: Acceleration depends on change in velocity. Since velocity has both magnitude and direction, acceleration is also a vector quantity.

4. Long Answer Questions

Q1. Define average acceleration and derive its formula.

Average acceleration is the change in velocity divided by time interval.

If initial velocity = u
Final velocity = v
Time taken = Δt

Change in velocity:

Δv = v - u

Therefore,

a = Δv / Δt

Answer: Average acceleration is equal to change in velocity divided by time interval.

Q2. Explain instantaneous acceleration.

Instantaneous acceleration is acceleration at a particular instant of time. It is obtained when the time interval becomes extremely small.

a = dv / dt

Answer: Instantaneous acceleration gives exact acceleration at any instant.

5. Assertion and Reason Questions

Q1.

Assertion (A): Acceleration is a vector quantity.
Reason (R): Acceleration depends on change in velocity.

A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation
C. A is true but R is false
D. A is false but R is true

Answer: A

6. Fill in the Blanks

1. Acceleration is the rate of change of _______.

Answer: velocity

2. SI unit of acceleration is _______.

Answer: m/s²

3. Negative acceleration is called _______.

Answer: retardation

7. Case Study Questions

A car moves along a straight road. Its velocity changes from 10 m/s to 30 m/s in 5 seconds.

Q1. What is the change in velocity?

Answer: 20 m/s

Q2. Calculate acceleration.

a = (v - u)/t

a = (30 - 10)/5 = 4 m/s²

Answer: 4 m/s²

8. Statement Based Questions

Q1. Acceleration can exist without change in speed.

Answer: True

Q2. A body moving in circular path has acceleration.

Answer: True

Q3. Velocity and acceleration always act in same direction.

Answer: False

9. Match the Columns

Column A Column B
1. Acceleration a. m/s²
2. Velocity b. Vector quantity
3. Retardation c. Negative acceleration
4. SI unit of acceleration d. Rate of change of displacement

Answers:
1 → b
2 → d
3 → c
4 → a

10. Important Formula Questions

Q1. Write formula for average acceleration.

a = Δv / Δt

Q2. Write formula for instantaneous acceleration.

a = dv / dt

Q3. Write acceleration components in x and y directions.

ax = dvx/dt
ay = dvy/dt

Internal Links
Motion in a Straight Line Notes
Motion in a Plane Notes
Velocity and Speed Difference
Vector Quantities in Physics
Newton’s Laws of Motion
Kinematics Formula Sheet
NEET Physics Important Questions
CBSE Class 11 Physics Chapter Wise Notes
Projectile Motion Notes
Units and Dimensions Notes

Saturday, May 16, 2026

Class 11 Physics Motion in a Straight Line Notes and Questions

 

NCERT Physics Class 11 Chapter 2 Easy Line-by-Line Notes 

- Dr.Sanjaykumar pawar

Area Under Velocity-Time Graph


Fig. 2.4 Explanation

“Area under v–t curve equals displacement...”

Very Important Concept

On a velocity-time graph:

Displacement=\text{Area under v-t graph}


“The v–t curve is a straight line parallel to the time axis...”

Meaning

  • Velocity remains constant.

  • Object moves with uniform velocity.


“Area under it between t = 0 and t = T is the area of rectangle...”

Graph Shape

Rectangle:

  • Height = velocity (u)

  • Base = time (T)


Rectangle Area

Area=u\times T

Since:

  • area under graph = displacement

Therefore:

x=uT


“How come area equals distance?”

Dimensional Understanding

Velocity × Time:

[
(m/s)\times s = m
]

So result becomes displacement.


Important Note About Graphs

“x–t, v–t and a–t graphs shown have sharp kinks...”

Meaning

Some graphs in textbooks have sharp corners.

But in real life:

  • motion changes smoothly.


“Acceleration and velocity cannot change abruptly...”

Important Physical Meaning

Objects cannot instantly jump from:

  • slow to very fast

  • or stop suddenly

Changes are continuous.


2.4 Kinematic Equations for Uniformly Accelerated Motion


“For uniformly accelerated motion...”

Meaning

Acceleration remains constant.

Example:

  • freely falling object


Variables Used

SymbolMeaning
(x)displacement
(t)time
(v_0)initial velocity
(v)final velocity
(a)acceleration

First Equation of Motion

“Equation already obtained gives relation between final and initial velocities...”

v=v_0+at

Meaning

Final velocity:

initial velocity + change due to acceleration


Graphical Representation

“This relation is graphically represented in Fig. 2.5.”

Meaning

Velocity-time graph becomes a straight line.

Reason:

  • acceleration is constant.


Area Under Graph

“Area between instants 0 and t = area of triangle + rectangle”

Total displacement:

=
rectangle area + triangle area






Second Equation of Motion

Meaning

Displacement depends on:

  • initial velocity

  • acceleration

  • time


Average Velocity Form

Meaning

For constant acceleration:

Average velocity

mean of initial and final velocities.


Important Condition

“Constant acceleration only”

This formula works only when:

  • acceleration remains constant.


Third Equation of Motion


Meaning of Third Equation

This equation connects:

  • velocity

  • displacement

  • acceleration

without using time.


Three Main Equations of Motion





Graph Concepts Summary

Graph  Slope Gives  Area Gives
Position-Time  Velocity     —
Velocity-Time    Acceleration    Displacement

Real-Life Examples





One-Line Summary

For uniformly accelerated motion, displacement and velocity can be calculated using three important equations derived from the velocity-time graph. 

KINEMATIC EQUATIONS FOR UNIFORMLY ACCELERATED MOTION

├── Velocity-Time Graph

│   ├── Area under graph = displacement

│   ├── Constant velocity graph

│   │   └── Horizontal straight line

│   └── Uniform acceleration graph

│       └── Sloping straight line

├── Area Under v-t Graph

│   ├── Rectangle area

│   │     displacement = velocity × time

│   ├── Formula

│   │     x = uT

│   └── Unit check

│         (m/s) × s = m

├── Important Physical Idea

│   ├── Velocity changes continuously

│   ├── Acceleration changes continuously

│   └── Real motion graphs are smooth

├── Uniformly Accelerated Motion

│   ├── Constant acceleration

│   └── Variables

│       ├── x → displacement

│       ├── t → time

│       ├── v₀ → initial velocity

│       ├── v → final velocity

│       └── a → acceleration

├── First Equation of Motion

│   ├── Formula

│   │     v = v₀ + at

│   ├── Gives final velocity

│   └── Used when time is known

├── Displacement from Graph

│   ├── Total area

│   │     = rectangle + triangle

│   │

│   ├── Rectangle area

│   │     = v₀t

│   │

│   ├── Triangle area

│   │     = 1/2 (v - v₀)t

│   │

│   └── Total displacement

│         x = v₀t + 1/2 (v - v₀)t

├── Second Equation of Motion

│   ├── Using

│   │     v - v₀ = at

│   ├── Formula

│   │     x = v₀t + 1/2 at²

│   └── Used for displacement

├── Average Velocity

│   ├── Formula

│   │     v_avg = (v + v₀)/2

│   ├── Works only for constant acceleration

│   └── Displacement form

│         x = [(v + v₀)/2] t

├── Third Equation of Motion

│   ├── Formula

│   │     v² = v₀² + 2ax

│   ├── Time not required

│   └── Relates

│       ├── velocity

│       ├── displacement

│       └── acceleration

├── Three Main Equations

│   │

│   ├── First

│   │     v = v₀ + at

│   │

│   ├── Second

│   │     x = v₀t + 1/2 at²

│   │

│   └── Third

│         v² = v₀² + 2ax

├── Graph Rules

│   ├── Position-Time Graph

│   │   └── Slope = velocity

│   │

│   └── Velocity-Time Graph

│       ├── Slope = acceleration

│       └── Area = displacement

├── Real-Life Examples

│   ├── Accelerating car

│   ├── Falling object

│   ├── Braking vehicle

│   └── Train gaining speed

└── Key Ideas

    ├── Constant acceleration simplifies motion

    ├── Area under v-t graph gives displacement

    └── Equations of motion describe straight-line motion 

Internal Links

  1. Class 11 Physics Units and Measurements Notes
  2. Class 11 Physics Laws of Motion Notes
  3. Class 11 Physics Work Energy and Power Questions
  4. Kinematics Formula Sheet PDF
  5. CBSE Class 11 Physics Important Numericals
  6. Class 11 Physics Chapter Wise MCQs
  7. Motion in a Plane Complete Notes
  8. Physics Graphs and Derivations Guide
  9. NCERT Solutions for Class 11 Physics
  10. Physics Assertion Reason Questions Collection


Class 11 Physics Question Bank

CBSE Class 11 Physics Question Bank

Chapter: Motion in a Straight Line

1. Multiple Choice Questions (MCQs)

1. Motion is defined as:
  • A. Change in mass
  • B. Change in position with time
  • C. Change in force
  • D. Change in shape
Answer: B. Change in position with time
2. SI unit of acceleration is:
  • A. m/s
  • B. m/s²
  • C. km/h
  • D. m²/s
Answer: B. m/s²
3. Area under velocity-time graph gives:
  • A. Velocity
  • B. Acceleration
  • C. Displacement
  • D. Speed
Answer: C. Displacement

2. Very Short Answer Questions

1. Define motion.
Motion is the change in position with time.
2. Define acceleration.
Acceleration is the rate of change of velocity with time.
3. Write SI unit of velocity.
m/s

3. Short Answer Questions

1. Differentiate between speed and velocity.
Speed Velocity
Scalar quantity Vector quantity
No direction Has direction
Only magnitude Magnitude and direction
2. Write formula of average velocity.
v = Δx / Δt
Average velocity is displacement divided by time.

4. Long Answer Questions

1. Derive second equation of motion.
v = u + at
s = ut + 1/2 at²
The second equation of motion is obtained from velocity-time graph by calculating area under the graph.

5. Assertion and Reason Questions

Assertion: Slope of velocity-time graph gives acceleration.
Reason: Acceleration is rate of change of velocity with time.
Both Assertion and Reason are true and Reason correctly explains Assertion.
Assertion: Speed can be negative.
Reason: Speed is scalar quantity.
Assertion is false but Reason is true.

6. Fill in the Blanks

1. Motion is change in ______ with time.
position
2. SI unit of acceleration is ______.
m/s²
3. Area under velocity-time graph gives ______.
displacement

7. Statement Based Questions

Statement I: Velocity has direction.
Statement II: Speed has no direction.
Both statements are true.
Statement I: Uniform motion means constant velocity.
Statement II: Acceleration is zero in uniform motion.
Both statements are true.

8. Match the Columns

Column A Column B
Slope of x-t graph Velocity
Slope of v-t graph Acceleration
Area under v-t graph Displacement
Constant velocity Zero acceleration

9. Case Study Questions

A car starts from rest and accelerates uniformly at 2 m/s² for 5 seconds.
  1. Find final velocity.
  2. Find displacement.
v = u + at
v = 0 + (2)(5) = 10 m/s
s = ut + 1/2 at²
s = 0 + 1/2(2)(25) = 25 m
Final velocity = 10 m/s
Displacement = 25 m

10. Important Formulas

v = u + at
s = ut + 1/2 at²
v² = u² + 2as
a = (v - u)/t
Educational infographic showing Class 11 Physics Motion in a Straight Line concepts including velocity, acceleration, equations of motion, and velocity-time graphs.
Class 11 Physics Motion in a Straight Line notes, formulas, graphs, and important CBSE exam questions.


Uniformly Accelerated Motion Class 11 Physics Notes | NEET & JEE MCQs

 - Dr.Sanjaykumar Pawar   Uniformly Accelerated Motion (1-D) Physics Notes, Formulas & NEET Questions  Uniformly Accelerated Motion (1-D...