NEET Unit Conversion Practice Questions with Answers | MCQ + Assertion Reason + PYQ

 - Dr.Sanjaykumar Pawar  

CBSE & NEET Physics Unit Conversion Notes, Tricks, MCQs & Shortcuts 

NEET Physics Unit Conversion Chart with formulas, shortcuts, and memory tricks for fast exam revision.

🔗 Internal Links 

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Unit Conversion in Physics (CBSE Class 11)

1.2 Fill in the blanks by suitable conversion of units

(a) 1 kg m² s⁻² = ______ g cm² s⁻²

Step 1: 1 kg = 10³ g
Step 2: 1 m² = (10² cm)² = 10⁴ cm²
Step 3: Multiply
= 10³ × 10⁴ g cm² s⁻²
= 10⁷ g cm² s⁻²

(b) 1 m = ______ ly

1 light year = 9.46 × 10¹⁵ m
1 m = 1 / (9.46 × 10¹⁵) ly
= 1.06 × 10⁻¹⁶ ly

(c) 3.0 m s⁻² = ______ km h⁻²

Step 1: 1 m = 10⁻³ km → 3.0 m s⁻² = 3.0 × 10⁻³ km s⁻²
Step 2: 1 s⁻² = (3600)² h⁻² = 1.296 × 10⁷ h⁻²
Step 3: Multiply
= 3.0 × 10⁻³ × 1.296 × 10⁷
= 3.89 × 10⁴ km h⁻²

(d) G = 6.67 × 10⁻¹¹ N m² kg⁻² = ______ cm³ s⁻² g⁻¹

1 N = 1 kg m s⁻²
So, N m² kg⁻² = m³ s⁻² kg⁻¹

Convert units:
1 m³ = 10⁶ cm³
1 kg⁻¹ = 10⁻³ g⁻¹

Multiply factors:
= 10⁶ × 10⁻³ = 10³
= 6.67 × 10⁻¹¹ × 10³
= 6.67 × 10⁻⁸ cm³ s⁻² g⁻¹

Short Notes: Conversion of Units

1. Concept

Unit conversion is the process of expressing a physical quantity in different units without changing its value.

2. Basic Conversions

- 1 kg = 10³ g
- 1 m = 10² cm
- 1 km = 10³ m
- 1 h = 3600 s
- 1 ly = 9.46 × 10¹⁵ m

3. Derived Units

- Force: 1 N = 1 kg m s⁻²
- Energy: 1 J = 1 kg m² s⁻²
- Gravitational constant: G = N m² kg⁻² = m³ s⁻² kg⁻¹

4. Method

1. Write given quantity
2. Replace units with conversions
3. Apply powers correctly
4. Multiply and simplify

5. Important Tips

- Always use powers of 10
- Treat units like algebra
- Check final unit carefully

📘 Unit Conversion Master Structure (NEET + CBSE)

📊 1. Basic Conversion Table

Quantity	SI Unit	Conversion
Mass	kg	1 kg = 10³ g
Length	m	1 m = 10² cm
Length	km	1 km = 10³ m
Time	hour	1 h = 3600 s
Force	Newton	1 N = 1 kg m s⁻²
Energy	Joule	1 J = 1 kg m² s⁻²
Gravitational Constant	G	N m² kg⁻²

🌟 2. Power Conversion Rules

Base Unit	Conversion Power
m → cm	10²
m² → cm²	10⁴
m³ → cm³	10⁶
kg → g	10³
s → h	3600
s⁻² → h⁻²	(3600)²

🧠 3. Mnemonic Trick

Mnemonic: “M K G H L J N G”

Meaning:
M → Meter
K → Kilometer
G → Gram
H → Hour
L → Light Year
J → Joule
N → Newton
G → Gravitational Constant

Memory Line:
“My King Gives High Level Job New Goals”

⚡ 4. Fast Solving Method

STEP 1 → Convert each unit separately
STEP 2 → Apply power rules carefully
STEP 3 → Multiply all factors of 10
STEP 4 → Write final answer in scientific notation

Shortcut:
“One unit at a time + power rule = fast solution”

🧪 NEET Practice Questions - Unit Conversion & Dimensions

🟢 1. Direct MCQs (Single Correct Option)

Q1. 1 kg m² s⁻² is equal to:
A) 10⁵ g cm² s⁻²
B) 10⁷ g cm² s⁻²
C) 10⁶ g cm² s⁻²
D) 10⁸ g cm² s⁻²

Answer: B

Q2. 1 m is equal to:
A) 10⁻¹⁵ ly
B) 10⁻¹⁶ ly
C) 10⁻¹⁴ ly
D) 10⁻¹³ ly

Answer: B

Q3. 3 m s⁻² equals:
A) 3.9 × 10³ km h⁻²
B) 3.9 × 10⁴ km h⁻²
C) 3.9 × 10⁵ km h⁻²
D) 3.9 × 10² km h⁻²

Answer: B

Q4. SI unit of G is:
A) N m² kg⁻²
B) kg m³ s⁻²
C) m² s⁻² kg
D) N m kg⁻²

Answer: A

🟡 2. Statement-Based Questions

Q5. Statement I: 1 m³ = 10⁶ cm³
Statement II: Volume depends on cube of length
A) Both true, II explains I
B) Both true, II not explanation
C) I true, II false
D) I false, II true

Answer: A

Q6. Statement I: 1 N = 1 kg m s⁻²
Statement II: Newton is derived unit
A) Both true, II explains I
B) Both true, II not explanation
C) I false, II true
D) I true, II false

Answer: A

🔴 3. Assertion & Reason

Q7.
A: 1 m² = 10⁴ cm²
R: Area depends on square of length
A) Both true, R explains A
B) Both true, R not explanation
C) A true, R false
D) A false, R true

Answer: A

Q8.
A: G has dimensions L³ M⁻¹ T⁻²
R: G = N m² kg⁻²
A) Both true, R explains A
B) Both true, R not explanation
C) A false, R true
D) A true, R false

Answer: A

🔵 4. Match the Columns

Column A	Column B
1 N	kg m s⁻²
1 m²	10⁴ cm²
1 J	kg m² s⁻²
1 kg	10³ g

Answer: A-2, B-1, C-3, D-4

🔥 5. Hard Questions

Q12. Convert 5 m s⁻² into km h⁻²
A) 5.4 × 10⁴
B) 6.2 × 10⁴
C) 4.8 × 10⁴
D) 3.6 × 10⁴

Answer: A

Q13. 1 m in light year:
A) 10⁻¹⁵ ly
B) 10⁻¹⁶ ly
C) 10⁻¹⁴ ly
D) 10⁻¹³ ly

Answer: B

🧠 Exam Tips

✔ Convert stepwise
✔ Square and cube units carefully
✔ Use scientific notation
✔ Check final dimensions
✔ Avoid skipping steps

🧩 5. Concept Flow

Physical Quantity → Base Units (kg, m, s) → Derived Units (N, J, G) → Conversion Factors (10ⁿ) → Final Answer

🔥 6. Exam Strategy

✔ Convert step by step
✔ Always check power of units
✔ Use scientific notation
✔ Verify final dimensions
✔ Avoid skipping steps in NEET

🏆 Final Formula

Convert separately → Apply power → Multiply → Verify unit

Distance and Displacement NEET Notes with Practice Questions and Answers

- Dr.Sanjaykumar Pawar  

NEET Physics Distance Displacement Speed Velocity Complete Notes PDF 

Distance and Displacement in Physics explained with diagrams, formulas, speed, velocity, and NEET practice questions.

 Internal Links

Motion in a Straight Line Notes

Speed and Velocity Notes

Instantaneous Velocity and Acceleration Notes

Introduction to Vectors in Physics

Vector Addition and Subtraction

Kinematics Important Questions for NEET

Class 11 Physics Motion Notes

NEET Physics MCQ Collection

Assertion Reason Questions for NEET Physics

NEET Physics Numericals Practice Set

Average Speed and Average Velocity Problems

Previous Year NEET Physics Questions

Acceleration Complete Notes

One Dimensional Motion Notes

NCERT Kinematics Solutions

NEET Physics Short Notes

Distance, Displacement, Speed and Velocity

1. Distance

• Total path length covered by a body.
• Scalar quantity.
• Always positive or zero.
• SI Unit: metre (m).

2. Displacement

• Shortest distance between initial and final positions with direction.
• Vector quantity.
• Can be positive, negative, or zero.
• SI Unit: metre (m).

Displacement = Final Position − Initial Position

Important Cases

Case 1: Straight Line Motion (No Turning)

• Distance ≠ 0
• Displacement ≠ 0
• Distance = Displacement

Case 2: Returning to Starting Point

• Distance > 0
• Displacement = 0

Example: 5 m forward + 5 m backward

• Distance = 10 m
• Displacement = 0 m

Important Relation

Distance ≥ |Displacement|

• Distance can be greater than displacement ✔
• Distance can never be less than displacement ✘

Speed

• Rate of change of distance.
• Scalar quantity.
• Always positive.

Speed = Distance / Time

Velocity

• Rate of change of displacement.
• Vector quantity.

Velocity = Displacement / Time

Average Speed

Average Speed = Total Distance / Total Time

Average Velocity

Average Velocity = Total Displacement / Total Time

Quick Revision Table

Quantity	Type	Can be Zero?	Can be Negative?
Distance	Scalar	Yes	No
Displacement	Vector	Yes	Yes
Speed	Scalar	Yes	No
Velocity	Vector	Yes	Yes

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NEET Practice Questions with Answers

MCQs

Q1. A body moves 10 m east and then 6 m west. What is the displacement?
A) 16 m
B) 10 m
C) 4 m east
D) 4 m west

Answer: C) 4 m east

Q2. Which quantity is always positive?
A) Velocity
B) Displacement
C) Distance
D) Acceleration

Answer: C) Distance

Q3. A runner completes one lap of a circular track and returns to the starting point. The displacement is:
A) Radius
B) Diameter
C) Circumference
D) Zero

Answer: D) Zero

Q4. Which relation is always true?
A) Distance < Displacement
B) Distance = 0, Displacement ≠ 0
C) Distance ≥ |Displacement|
D) Distance ≤ |Displacement|

Answer: C) Distance ≥ |Displacement|

Q5. Velocity is the rate of change of:
A) Distance
B) Time
C) Position/Displacement
D) Speed

Answer: C) Position/Displacement

Assertion and Reason

Q6. Distance can never be less than displacement.
Reason: Displacement is the shortest distance between initial and final positions.

Answer: Both are true and Reason correctly explains Assertion.

Q7. A body can have zero displacement and non-zero distance.
Reason: The body may return to its starting point.

Answer: Both are true and Reason correctly explains Assertion.

Numerical Problems

Q8. A person walks 12 m north and then 5 m south.
Find distance and displacement.

Distance = 17 m
Displacement = 7 m north

Q9. A car travels 40 km east and then 30 km west.
Find distance and displacement.

Distance = 70 km
Displacement = 10 km east

Q10. A body completes one revolution on a circular track of circumference 200 m.

Distance = 200 m
Displacement = 0 m

Speed and Velocity Numericals

Q11. A car covers 120 km in 2 hours. Find average speed.

Average Speed = 120 / 2 = 60 km/h

Q12. A body moves 30 m east and then 10 m west in 10 s. Find average velocity.

Displacement = 20 m east
Average Velocity = 20 / 10 = 2 m/s east

True / False

Q13. Distance is a vector quantity.

False

Q14. Displacement may be zero.

True

Q15. Average speed is always greater than or equal to magnitude of average velocity.

True

Q16. Distance can be negative.

False

Statement Based Questions

Q17. Which statements are correct?
1. Distance is scalar.
2. Displacement is vector.
3. Distance can be zero while displacement is non-zero.
4. Displacement can be zero while distance is non-zero.

Answer: 1, 2 and 4 only

Q18. A particle moves 5 m east and 12 m north. Find displacement.

Displacement = √(5² + 12²)
= √169 = 13 m

Conceptual Questions

Q19. Can displacement be greater than distance?

No

Q20. Can distance and displacement be equal?

Yes, when motion is in a straight line without changing direction.

Concept of Rest and Motion, Distance & Displacement Notes and MCQs for NEET

 - Dr.Sanjaykumar Pawar  

Rest and Motion Class 11 Physics Notes with NEET Practice Questions

Rest and Motion, Distance and Displacement explained with examples and NEET practice questions.

 Internal Links

Motion in a Straight Line Notes

Instantaneous Velocity and Acceleration Notes

Speed vs Velocity Explained

Introduction to Vectors in Physics

Vector Addition and Subtraction

Position-Time Graphs Explained

Acceleration and Retardation Notes

NCERT Class 11 Kinematics Solutions

Important NEET Physics MCQs

Assertion-Reason Questions for NEET

Physics Numericals for Class 11

Motion in One Dimension Revision Notes

Previous Year NEET Physics Questions

Units and Measurements Notes

Errors and Significant Figures MCQs

NEET Physics Notes

Concept of Rest and Motion

A. Rest and Motion are Relative Terms

• Rest and motion depend on the observer.
• The same object can be at rest for one observer and in motion for another observer.

Example: A person B is sitting inside a moving bus.

• For observer A (inside the bus), B is at rest.
• For observer C (standing on the road), B is in motion.

Conclusion: Rest and motion are relative terms.

B. Definitions

Rest

A body is said to be at rest if its position does not change with time with respect to the observer.

Motion

A body is said to be in motion if its position changes with time with respect to the observer.

---

Distance and Displacement

1. Distance (S)

Definition:

Distance is the actual path length travelled by a body from its initial position to its final position.

Properties:

• Distance is a scalar quantity.
• It has magnitude only.
• It is path dependent.
• It is denoted by S.
• Distance is always positive.

Examples:

• 7 m right + 2 m left → Distance = 9 m
• 5 m + 5 m + 4 m → Distance = 14 m
• 5 m right + 5 m left → Distance = 10 m

2. Displacement

Definition:

Displacement is the shortest straight-line distance between the initial and final positions of a body.

Properties:

• Displacement is a vector quantity.
• It has magnitude and direction.
• It depends only on initial and final positions.
• It may be positive, negative, or zero.
• Magnitude of displacement is always less than or equal to distance.

Formula:

|Displacement| ≤ Distance

Distance vs Displacement

Distance	Displacement
Scalar Quantity	Vector Quantity
Path Dependent	Path Independent
Always Positive	Can be Positive, Negative, or Zero
Actual Path Length	Shortest Distance

NEET Tip: If a body returns to its starting point, displacement becomes zero but distance remains non-zero.

---

NEET Practice Questions

Section A: Conceptual MCQs

1. A passenger sitting in a moving train is at rest with respect to:
(a) Trees outside the train
(b) Person on platform
(c) Another passenger sitting beside him
(d) Railway track
Answer: (c)

2. Rest and motion are:
(a) Absolute terms
(b) Relative terms
(c) Scalars
(d) Vectors
Answer: (b)

3. A body can be:
(a) At rest for all observers
(b) In motion for all observers
(c) At rest for one observer and in motion for another
(d) None
Answer: (c)

4. Which is a scalar quantity?
(a) Displacement
(b) Velocity
(c) Acceleration
(d) Distance
Answer: (d)

5. Which quantity depends on path followed?
(a) Displacement
(b) Distance
(c) Position Vector
(d) None
Answer: (b)

Section B: Distance and Displacement

6. A particle moves 10 m east and then 10 m west. Distance travelled is:
(a) 0 m
(b) 10 m
(c) 20 m
(d) 5 m
Answer: (c)

7. For Question 6, displacement is:
(a) 20 m
(b) 10 m
(c) 0 m
(d) 5 m
Answer: (c)

8. A body moves 3 m east and then 4 m north. Magnitude of displacement is:
(a) 5 m
(b) 7 m
(c) 1 m
(d) 12 m
Answer: (a)

9. Distance can never be:
(a) Positive
(b) Zero
(c) Negative
(d) Equal to displacement
Answer: (c)

10. Magnitude of displacement is always:
(a) Greater than distance
(b) Equal to or less than distance
(c) Equal to distance only
(d) Less than distance only
Answer: (b)

Assertion-Reason Questions

11. Assertion: Distance is a scalar quantity.
Reason: Distance has magnitude but no direction.
Answer: Both are true and Reason is correct explanation.

12. Assertion: Displacement can be zero even if distance is non-zero.
Reason: Returning to starting point gives zero displacement.
Answer: Both are true and Reason is correct explanation.

Numerical Questions

13. A boy walks 8 m east and then 6 m west.
Distance = ?
Displacement = ?
Distance = 14 m
Displacement = 2 m east

14. A particle moves 5 m north and 12 m east.
Distance = ?
Displacement = ?
Distance = 17 m
Displacement = 13 m

15. A runner completes one circular track of radius 14 m.
Distance = 88 m
Displacement = 0 m

NEET Challenge Questions

16. A particle moves along a semicircle of radius r. Ratio of distance to displacement is:
(a) π : 2
(b) 2 : π
(c) π² : 2
(d) 2π : 1
Answer: (a)

17. Which statement is correct?
(a) Distance can be zero while displacement is non-zero
(b) Distance can never be less than displacement
(c) Displacement is always greater than distance
(d) Distance and displacement are always equal
Answer: (b)

18. A man walks 4 m east, 3 m north, 4 m west and 3 m south.
Distance travelled?
Answer: 14 m

19. For Question 18, displacement is:
(a) 14 m
(b) 7 m
(c) 0 m
(d) 1 m
Answer: (c)

20. A particle moves 6 m east, 8 m north and 10 m west.
Magnitude of displacement?
(a) 4 m
(b) 8 m
(c) 4√5 m
(d) 10 m
Answer: (c)

---

Quick Revision

• Rest and motion are relative.
• Distance → Scalar, Path Dependent.
• Displacement → Vector, Path Independent.
• Distance ≥ Displacement.
• Round Trip → Displacement = 0.
• Distance is never negative.
• Displacement can be positive, negative, or zero.

Equilibrium of a Particle Class 11 Physics Notes, MCQs, Questions and Answers

 Equilibrium of a Particle Class 11 CBSE Notes with Question Bank

Equilibrium of a Particle showing balanced forces, vector addition, and equilibrium conditions in Class 11 Physics.

-  Dr.Sanjaykumar Pawar 

Internal Links

Units and Measurements Class 11 Physics Notes

Motion in a Straight Line Notes

Motion in a Plane Notes

Laws of Motion Complete Notes

Free Body Diagram Explained

Force and Friction Notes

Vector Addition and Resolution of Vectors

Work, Energy and Power Notes

System of Particles and Rotational Motion

Gravitation Class 11 Notes

Mechanical Properties of Solids

Mechanical Properties of Fluids

Oscillations and Waves Notes

Class 11 Physics MCQ Collection

NCERT Solutions Class 11 Physics

CBSE Class 11 Physics Important Questions

NEET Physics Revision Notes

Assertion Reason Questions for Physics

Case Study Questions for Class 11 Physics

Physics Formula Sheet Class 11

Equilibrium of a Particle (NEET Level Notes)

1. Meaning of Equilibrium

• Equilibrium means a body is balanced under the action of forces.
• A particle is said to be in equilibrium when the net external force acting on it is zero.
• The resultant force acting on the particle becomes zero.

ΣF = 0

• Here, ΣF represents the vector sum of all forces acting on the particle.

2. Condition of Equilibrium

• If the resultant of all forces is zero, the particle is in equilibrium.
• According to Newton's First Law of Motion:

• The particle may remain at rest.
• The particle may move with constant velocity.

Important: Zero net force does not always mean the object is at rest. It can also move with uniform velocity.

3. Equilibrium Under Two Forces

Suppose two forces F₁ and F₂ act on a particle.

F₁ = −F₂

Conditions

• The two forces must have equal magnitude.
• The two forces must act in opposite directions.
• The two forces must act along the same straight line.

Example

• A book resting on a table.
• Weight acts downward.
• Normal reaction acts upward.
• Both forces are equal and opposite.
• Hence the book remains in equilibrium.

4. Equilibrium Under Three Concurrent Forces

Concurrent forces are forces whose lines of action pass through the same point.

Suppose three forces F₁, F₂ and F₃ act on a particle.

F₁ + F₂ + F₃ = 0

Meaning

• The vector sum of all three forces is zero.
• The resultant of any two forces is equal and opposite to the third force.

5. Triangle Law of Equilibrium

• Three forces in equilibrium can be represented by the three sides of a triangle.
• The vectors should be drawn head-to-tail in the same order.
• The triangle formed should be closed.
• A closed triangle indicates zero resultant force.

Three concurrent forces are in equilibrium if they can be represented completely by the sides of a triangle taken in order.

6. Equilibrium Under Many Forces

Suppose many forces F₁, F₂, F₃, ... Fn act on a particle.

F₁ + F₂ + F₃ + ... + Fn = 0

Polygon Law of Equilibrium

• If all forces can be represented by the sides of a closed polygon, the particle is in equilibrium.
• The arrows of all vectors should be taken in the same order.
• The resultant force becomes zero.

Remember

• Closed Triangle → Three Forces
• Closed Polygon → Many Forces

7. Equilibrium in Terms of Components

Every force can be resolved into components along x, y and z directions.

• F₁x = x-component of force F₁
• F₁y = y-component of force F₁
• F₁z = z-component of force F₁

For equilibrium, the sum of force components along each axis must be zero.

Along X-axis

F₁x + F₂x + F₃x = 0

Along Y-axis

F₁y + F₂y + F₃y = 0

Along Z-axis

F₁z + F₂z + F₃z = 0

8. Physical Meaning of Component Equations

• Forces along +x and −x directions balance each other.
• Forces along +y and −y directions balance each other.
• Forces along +z and −z directions balance each other.
• Hence no acceleration is produced in any direction.

9. NEET Quick Revision Table

Situation	Condition for Equilibrium
Two Forces	Equal and Opposite
Three Forces	Closed Triangle
Many Forces	Closed Polygon
X-direction	ΣFx = 0
Y-direction	ΣFy = 0
Z-direction	ΣFz = 0
Net Force	ΣF = 0

NEET Summary: A particle is said to be in equilibrium when the vector sum of all external forces acting on it is zero (ΣF = 0). In equilibrium, the particle remains either at rest or moves with constant velocity.

Equilibrium of a Particle - Mind Map (Plain Text Tree)

EQUILIBRIUM OF A PARTICLE │ ├── Definition │ │ │ ├── Net external force = 0 │ ├── Resultant force = 0 │ └── ΣF = 0 │ ├── According to Newton's First Law │ │ │ ├── Particle remains at rest │ └── Particle moves with uniform velocity │ ├── Equilibrium Under Two Forces │ │ │ ├── F₁ = −F₂ │ ├── Equal magnitude │ ├── Opposite direction │ └── Same line of action │ ├── Equilibrium Under Three Forces │ │ │ ├── F₁ + F₂ + F₃ = 0 │ ├── Concurrent forces │ ├── Resultant of two forces │ │ = Opposite of third force │ └── Vector sum = 0 │ ├── Triangle Law of Equilibrium │ │ │ ├── Three forces form a triangle │ ├── Head-to-tail arrangement │ ├── Closed triangle │ └── Resultant force = 0 │ ├── Equilibrium Under Many Forces │ │ │ ├── F₁ + F₂ + F₃ + ... + Fn = 0 │ ├── Polygon Law │ ├── Closed polygon formed │ └── Resultant force = 0 │ ├── Resolution of Forces │ │ │ ├── Components along X-axis │ ├── Components along Y-axis │ └── Components along Z-axis │ ├── Conditions in Component Form │ │ │ ├── ΣFx = 0 │ ├── ΣFy = 0 │ └── ΣFz = 0 │ ├── Physical Meaning │ │ │ ├── Forces balance in X-direction │ ├── Forces balance in Y-direction │ ├── Forces balance in Z-direction │ └── No acceleration produced │ └── NEET Quick Facts │ ├── Two forces → Equal & Opposite ├── Three forces → Closed Triangle ├── Many forces → Closed Polygon ├── ΣFx = 0 ├── ΣFy = 0 ├── ΣFz = 0 └── ΣF = 0 ⇒ Equilibrium

CBSE Class 11 Physics

Equilibrium of a Particle - Question Bank

A. Multiple Choice Questions (MCQs)

1. A particle is said to be in equilibrium when:

(a) Velocity is zero

(b) Acceleration is zero

(c) Net force is zero

(d) Displacement is zero

Answer: (c) Net force is zero

2. If two forces keep a particle in equilibrium, they must be:

(a) Equal

(b) Opposite

(c) Equal and opposite

(d) Perpendicular

Answer: (c) Equal and opposite

3. The SI unit of force is:

(a) Joule

(b) Newton

(c) Watt

(d) Pascal

Answer: (b) Newton

4. For equilibrium in three dimensions:

(a) ΣFx = 0

(b) ΣFy = 0

(c) ΣFz = 0

(d) ΣFx = ΣFy = ΣFz = 0

Answer: (d)

5. Three concurrent forces in equilibrium form:

(a) Circle

(b) Triangle

(c) Rectangle

(d) Ellipse

Answer: (b) Triangle

B. Very Short Answer Questions (1 Mark)

1. What is equilibrium?

Answer: Equilibrium is the state when the net external force acting on a particle is zero.

2. Write the condition for equilibrium.

Answer: ΣF = 0

3. What is the resultant force on a particle in equilibrium?

Answer: Zero.

4. What are concurrent forces?

Answer: Forces whose lines of action meet at a single point.

5. Can a moving particle be in equilibrium?

Answer: Yes, if it moves with constant velocity.

C. Short Answer Questions (2–3 Marks)

1. State the conditions for equilibrium under two forces.

Answer:
1. Forces must be equal in magnitude.
2. Forces must act in opposite directions.
3. Forces must act along the same line.

2. Explain triangle law of equilibrium.

Answer: If three forces acting on a particle can be represented by the sides of a triangle taken in order, the particle is in equilibrium.

3. What are the component equations of equilibrium?

Answer:
ΣFx = 0
ΣFy = 0
ΣFz = 0

D. Long Answer Questions (5 Marks)

1. Explain equilibrium of a particle.

Answer: A particle is said to be in equilibrium when the vector sum of all external forces acting on it is zero.

Condition:
ΣF = 0

According to Newton's First Law:
• The particle remains at rest, or
• Moves with uniform velocity.

For three-dimensional equilibrium:
ΣFx = 0
ΣFy = 0
ΣFz = 0

All three conditions must be satisfied simultaneously.

2. Explain equilibrium under three concurrent forces.

Answer:
For three concurrent forces:
F₁ + F₂ + F₃ = 0

The resultant of any two forces is equal and opposite to the third force.

These forces can be represented by the sides of a closed triangle.

This is called Triangle Law of Equilibrium.

E. Assertion and Reason Questions

Assertion (A): A particle can move with constant velocity in equilibrium.
Reason (R): Net external force acting on it is zero.

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

Assertion (A): Three concurrent forces in equilibrium form a triangle.
Reason (R): Their vector sum is zero.

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

F. Fill in the Blanks

1. A particle is in equilibrium when the ______ force acting on it is zero.

Answer: resultant

2. According to Newton's ______ law, equilibrium implies rest or uniform motion.

Answer: first

3. Three forces in equilibrium form a closed ______.

Answer: triangle

4. Many forces in equilibrium form a closed ______.

Answer: polygon

G. Statement-Based Questions

Statement I: A particle in equilibrium may be moving.
Statement II: A particle in equilibrium has zero acceleration.

Answer: Both statements are true.

Statement I: Three forces in equilibrium form a closed triangle.
Statement II: Their vector sum is zero.

Answer: Both statements are true.

H. Match the Columns

Column A	Column B
1. Equilibrium	A. Closed Triangle
2. Three Forces	B. Net Force Zero
3. Polygon Law	C. Closed Polygon
4. Concurrent Forces	D. Meet at One Point

Answers
1 → B
2 → A
3 → C
4 → D

I. Case Study Questions

A signboard is hanging by two ropes. The forces acting on it are:

• Weight acting downward
• Tension T₁ in first rope
• Tension T₂ in second rope

The signboard remains at rest.

1. How many forces act on the signboard?

Answer: Three forces.

2. Is the signboard in equilibrium?

Answer: Yes.

3. What is the resultant force acting on it?

Answer: Zero.

4. Which law explains this equilibrium?

Answer: Newton's First Law of Motion.

5. Which geometric figure represents these forces?

Answer: Triangle.

J. HOTS Questions

1. Can a car moving with constant velocity be in equilibrium? Explain.

Answer: Yes. Constant velocity means zero acceleration. Therefore the net force acting on the car is zero and the car is in equilibrium.

2. Why is balancing of forces necessary for equilibrium?

Answer: Unbalanced forces produce acceleration. For equilibrium, acceleration must be zero. Therefore all forces must balance each other.

K. Important Formulae

ΣF = 0

ΣFx = 0

ΣFy = 0

ΣFz = 0

F₁ + F₂ + F₃ = 0

F₁ = −F₂