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Showing posts with label Vector Addition. Show all posts
Showing posts with label Vector Addition. Show all posts
Vectors Class 11 Physics Notes, MCQs, Assertion Reason, Case Study & CBSE Questions
Complete Class 11 Physics Vectors Notes with formulas, diagrams, MCQs, assertion-reason, case studies and CBSE exam questions.
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NEET Physics - Vectors Notes
NEET Physics Chapter : Vectors
Vectors are one of the most important topics in NEET Physics.
Almost every chapter uses vectors.
Therefore understanding vectors properly makes Mechanics very easy.
1. Equality of Vectors
Two vectors are called equal if
Magnitude is same.
Direction is same.
Position does NOT matter.
Even if vectors are shifted parallel,
they are still equal.
Equal vectors ⇒ Same Magnitude + Same Direction
2. Addition of Vectors
Vector addition means combining two vectors to get one resultant vector.
Triangle Law
Place the tail of second vector at the head of first vector.
Join the starting point to the final point.
That gives resultant.
Remember:
Head to Tail Rule
3. Parallelogram Law
If two vectors start from the same point,
complete a parallelogram.
Diagonal gives resultant vector.
Resultant = Diagonal of Parallelogram
4. Magnitude of Resultant
Suppose
First Vector = a
Second Vector = b
Angle between them = θ
R = √(a² + b² + 2ab cosθ)
This is one of the MOST IMPORTANT formulas for NEET.
Learn it perfectly.
5. Direction of Resultant
tanα =
(b sinθ)/(a + b cosθ)
α = angle made by resultant with first vector.
6. Special Cases
Angle
Magnitude
0°
a+b
180°
|a-b|
90°
√(a²+b²)
7. Example
Question:
Two vectors have equal magnitude A.
Angle between them is θ.
Find resultant.
Solution
R = √(A²+A²+2A²cosθ)
= √(2A²(1+cosθ))
Using
1+cosθ=2cos²(θ/2)
R = 2A cos(θ/2)
Resultant = 2A cos(θ/2)
Direction:
α = θ/2
The resultant bisects the angle between two equal vectors.
8. Memory Tricks
✔ Triangle Rule → Head to Tail
✔ Parallelogram Rule → Diagonal
✔ Equal Vectors → Same Magnitude + Same Direction
✔ 90° → Pythagoras
✔ 180° → Subtraction
✔ 0° → Addition
9. NEET Important Points
Magnitude is always positive.
Direction decides vector.
Vectors obey triangle law.
Resultant depends on angle.
Equal vectors can have different positions.
Parallelogram law is frequently asked in NEET.
10. Practice Questions
Define equal vectors.
State triangle law.
State parallelogram law.
Write magnitude formula.
Write direction formula.
Find resultant when angle is 90°.
Find resultant when angle is 180°.
Two vectors 10 N each make 60°. Find resultant.
Two vectors 5 N each make 120°. Find resultant.
Why does the resultant bisect equal vectors?
Summary
Equal vectors → Same magnitude + same direction
Triangle Law → Head to Tail
Parallelogram Law → Diagonal
Magnitude → √(a²+b²+2abcosθ)
Direction → tanα=(bsinθ)/(a+bcosθ)
Equal vectors → Resultant = 2Acos(θ/2)
Direction = θ/2
CBSE Class 11 Physics - Vectors Question Bank
CBSE Class 11 Physics
Chapter : Vectors Question Bank
1. Multiple Choice Questions (MCQs)
1. A vector quantity has
Only magnitude
Only direction
Magnitude and direction
None
Answer: C
2. Equal vectors have
Equal magnitude only
Equal direction only
Equal magnitude and direction
Different directions
Answer: C
3. The diagonal of a parallelogram represents
Difference of vectors
Resultant vector
Unit vector
Zero vector
Answer: B
2. Very Short Answer Questions (1 Mark)
Q1. Define a vector.
A quantity having both magnitude and direction is called a vector.
Q2. Give one example of a vector.
Velocity.
Q3. What is a zero vector?
A vector whose magnitude is zero.
3. Short Answer Questions (2-3 Marks)
Q1. Define equal vectors.
Two vectors having equal magnitude and same direction are called equal vectors.
Q2. State the triangle law of vector addition.
If two vectors are represented by two sides of a triangle taken in order, the third side taken in opposite order represents the resultant.
4. Long Answer Questions (5 Marks)
Q1. Explain the parallelogram law of vector addition with diagram.
If two vectors acting simultaneously are represented by two adjacent sides of a parallelogram, then the diagonal passing through the common point represents the resultant vector.
Magnitude:
R = √(A² + B² + 2AB cosθ)
Direction:
tanα = (B sinθ)/(A + B cosθ)
5. Assertion and Reason
Assertion:
Equal vectors may have different positions.
Reason:
A vector depends only on magnitude and direction.
Answer:
Both Assertion and Reason are true, and Reason correctly explains Assertion.
Assertion:
Scalar quantities have direction.
Reason:
Scalars possess only magnitude.
Answer:
Assertion is false.
Reason is true.
6. Fill in the Blanks
Question
Answer
A vector has ______ and ______.
Magnitude, Direction
The diagonal of a parallelogram gives the ______.
Resultant
A quantity having only magnitude is called ______.
Scalar
The SI unit of displacement is ______.
metre
7. Match the Columns
Column A
Column B
Velocity
Vector
Mass
Scalar
Acceleration
Vector
Time
Scalar
Answers
Velocity → Vector
Mass → Scalar
Acceleration → Vector
Time → Scalar
8. Statement Based Questions
Statement I:
The resultant of two equal vectors bisects the angle between them.
Statement II:
The magnitudes of both vectors are equal.
Both statements are true.
Statement II explains Statement I.
9. Case Study Questions
Rahul pushes a box with force 20 N towards east.
Aman pushes the same box with force 20 N making an angle of 60°.
Answer the following.
Parallelogram law showing resultant of two vectors A and B for Class 11 Physics.
-Dr.Sanjaykumar pawar Resultant of Two Vectors - NEET Notes
Example 3.2 - Resultant of Two Vectors
Example 3.2 Find the magnitude and
direction of the resultant of two vectors A
and B in terms of their magnitudes and
angle θ between them
Let two vectors be:
Vector A
Vector B
Angle between them = θ
We have to find:
Magnitude of resultant vector R
Direction of resultant vector
Step 1: Draw the vectors
Draw vector OP representing vector A.
Draw vector OQ representing vector B.
The angle between the vectors is θ.
Using the parallelogram law of vector addition, diagonal OS gives the resultant vector.
R = A + B
Step 2: Resolve vector B into components
Draw perpendicular SN on OP.
Now vector B has two components:
Horizontal Component
B cos θ
Vertical Component
B sin θ
Step 3: Find ON and SN
From geometry:
ON = OP + PN
But,
OP = A
PN = B cos θ
Therefore,
ON = A + B cos θ
Also,
SN = B sin θ
Step 4: Apply Pythagoras Theorem
In right triangle OSN:
OS² = ON² + SN²
Substituting values:
R² = (A + B cos θ)² + (B sin θ)²
Step 5: Expand the Equation
R² = A² + 2AB cos θ + B² cos² θ + B² sin² θ
Take B² common:
R² = A² + 2AB cos θ + B²(cos² θ + sin² θ)
Using identity:
sin² θ + cos² θ = 1
Therefore,
R² = A² + B² + 2AB cos θ
Final Formula for Magnitude
R = √(A² + B² + 2AB cos θ)
This formula gives the magnitude of the resultant vector.
This is called the Law of Cosines.
Direction of Resultant Vector
Let the resultant vector make angle α with vector A.
Step 6: Use Sine Relation
From triangle:
SN = R sin α
Also,
SN = B sin θ
Equating both:
R sin α = B sin θ
Therefore,
sin α = (B sin θ) / R
Step 7: Formula for tan α
From triangle:
tan α = SN / ON
Substitute values:
tan α = (B sin θ) / (A + B cos θ)
Important Results for NEET
Magnitude of Resultant
R = √(A² + B² + 2AB cos θ)
Direction of Resultant
tan α = (B sin θ) / (A + B cos θ)
Special Cases
1. When θ = 0°
R = A + B
2. When θ = 180°
R = |A - B|
3. When θ = 90°
R = √(A² + B²)
Quick Concept Summary
Resultant vector is found using parallelogram law.
Resolve vector B into horizontal and vertical components.
Apply Pythagoras theorem to find magnitude.
Magnitude formula comes from Law of Cosines.
Direction formula comes from trigonometric ratios.
CBSE Class 11 Physics - Vector Addition Questions
CBSE Class 11 Physics
Vector Addition - Important Questions and Answers
1. Multiple Choice Questions (MCQs)
Q1. The magnitude of resultant of two vectors A and B inclined at angle θ is:
A) A + B
B) A - B
C) √(A² + B² + 2AB cosθ)
D) √(A² + B²)
Answer: C) √(A² + B² + 2AB cosθ)
Q2. If two vectors act in the same direction, the resultant is:
A) A - B
B) A + B
C) AB
D) Zero
Answer: B) A + B
Q3. If angle between two vectors is 180°, the resultant is:
A) A + B
B) |A - B|
C) Zero
D) AB
Answer: B) |A - B|
2. Very Short Answer Questions
Q1. What is a resultant vector?
A single vector that represents the combined effect of two or more vectors is called resultant vector.
Q2. Which method is used to add two vectors geometrically?
Parallelogram law of vector addition.
Q3. What is the resultant when two vectors are perpendicular?
R = √(A² + B²)
Q4. At which angle is resultant maximum?
Resultant is maximum when angle is 0°.
3. Short Answer Questions
Q1. State parallelogram law of vector addition.
If two vectors acting simultaneously on a particle are represented by two adjacent sides of a parallelogram, then their resultant is represented by the diagonal of the parallelogram passing through the common point.
Q2. Write formula for magnitude of resultant vector.
R = √(A² + B² + 2AB cosθ)
Where:
A and B are magnitudes of vectors
θ is angle between them
Q3. Write formula for direction of resultant vector.
tanα = (B sinθ) / (A + B cosθ)
4. Long Answer Questions
Q1. Derive formula for magnitude of resultant vector.
Consider two vectors A and B inclined at angle θ.
Using parallelogram law:
R = A + B
Apply Pythagoras theorem:
R² = (A + B cosθ)² + (B sinθ)²
Expanding:
R² = A² + 2AB cosθ + B² cos²θ + B² sin²θ
Using identity:
sin²θ + cos²θ = 1
Therefore:
R² = A² + B² + 2AB cosθ
Hence,
R = √(A² + B² + 2AB cosθ)
Q2. Derive formula for direction of resultant vector.
From the triangle:
tanα = SN / ON
Where:
SN = B sinθ
ON = A + B cosθ
Therefore:
tanα = (B sinθ)/(A + B cosθ)
5. Assertion and Reason Questions
Q1.
Assertion (A): Resultant of two equal and opposite vectors is zero.
Reason (R): Opposite vectors cancel each other.
Both Assertion and Reason are true and Reason is the correct explanation.
Q2.
Assertion (A): Resultant of perpendicular vectors is equal to sum of vectors.
Reason (R): Pythagoras theorem is used for perpendicular vectors.
Assertion is false but Reason is true.
6. Fill in the Blanks
Q1. The diagonal of parallelogram gives the _________ vector.
Resultant
Q2. The formula for resultant vector uses law of _________.
Cosines
Q3. If θ = 0°, resultant is _________.
A + B
7. Case Study Questions
Two students are pulling a box using two ropes. One student applies force A and another applies force B making angle θ between them. The combined effect produces resultant force R.
Q1. Which law is used to find resultant force?
Parallelogram law of vector addition.
Q2. Write formula for resultant force.
R = √(A² + B² + 2AB cosθ)
Q3. What happens if both students pull with equal force in opposite directions?
Resultant force becomes zero.
8. Statement Based Questions
Q1.
Statement I: Vectors have magnitude and direction.
Statement II: Scalars have only magnitude.
Both statements are true.
Q2.
Statement I: Resultant depends on angle between vectors.
Statement II: Resultant is independent of vector magnitudes.