Laws of Motion — Previous Year Questions (Class 11 Physics)
Laws of Motion explain how forces change the motion of objects. Understand Newton's three laws and apply them to solve real-world problems involving fricti
TL;DR: Laws of Motion explain how forces change the motion of objects. Understand Newton's three laws and apply them to solve real-world problems involving f…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Laws of Motion explain how forces change the motion of objects. Understand Newton's three laws and apply them to solve real-world problems involving fricti
Laws of Motion — Previous Year Questions with Solutions
Q (2023, 3 marks): A car of mass 1000 kg is moving with a velocity of 20 m/s. A constant force of 2000 N is applied in the direction of motion for 5 seconds. Calculate the final velocity of the car.
Answer: Given:
m = 1000 kg
u = 20 m/s
F = 2000 N
t = 5 s
From Newton's second law:
F = ma
a = F/m = 2000/1000 = 2 m/s^2
Using v = u + at:
v = 20 + 2(5)
v = 20 + 10
v = 30 m/s
Final velocity = 30 m/s
Q (2022, 4 marks): Two blocks of masses 2 kg and 3 kg are placed on a frictionless horizontal surface. They are connected by a light string. A horizontal force of 15 N is applied to the 3 kg block. Find the acceleration of the system and the tension in the string.
Answer: Given:
m1 = 2 kg (first block)
m2 = 3 kg (second block)
F = 15 N (applied force)
Total mass = m1 + m2 = 2 + 3 = 5 kg
Acceleration of system:
F = (m1 + m2)a
15 = 5a
a = 3 m/s^2
For the 2 kg block (string pulls it):
T = m1 × a
T = 2 × 3
T = 6 N
Acceleration = 3 m/s^2, Tension = 6 N
Q (2024, 3 marks): A body of mass 5 kg is pushed along a frictionless horizontal surface with a force of 20 N. Calculate the acceleration produced and the distance covered in 4 seconds starting from rest.
Answer: Given:
m = 5 kg
F = 20 N
t = 4 s
u = 0 (starts from rest)
Acceleration:
F = ma
a = F/m = 20/5 = 4 m/s^2
Distance using s = ut + (1/2)at^2:
s = 0 + (1/2)(4)(4)^2
s = (1/2)(4)(16)
s = 32 m
Acceleration = 4 m/s^2, Distance = 32 m
Q (2023, 4 marks): A block of mass 10 kg is on an inclined plane at 30 degrees to the horizontal. If the coefficient of friction is 0.2, find the acceleration of the block down the plane.
Answer: Given:
m = 10 kg
θ = 30°
μ = 0.2
g = 10 m/s^2
Normal force: N = mg cos θ = 10 × 10 × cos 30° = 100 × (√3/2) = 50√3 N
Frictional force: f = μN = 0.2 × 50√3 = 10√3 N
Component of weight along plane: mg sin θ = 10 × 10 × sin 30° = 100 × 0.5 = 50 N
Net force down the plane: F_net = mg sin θ - f = 50 - 10√3 = 50 - 17.32 = 32.68 N
Acceleration: a = F_net/m = 32.68/10 = 3.27 m/s^2
Q (2022, 3 marks): A rope can withstand a maximum tension of 500 N. A mass of 40 kg is attached to the rope and lifted upward with an acceleration of 2 m/s^2. Will the rope break? (Take g = 10 m/s^2)
Answer: Given:
T_max = 500 N
m = 40 kg
a = 2 m/s^2 (upward)
g = 10 m/s^2
Applying Newton's second law (upward as positive):
T - mg = ma
T = m(g + a)
T = 40(10 + 2)
T = 40 × 12
T = 480 N
Since T = 480 N < T_max = 500 N, the rope will NOT break.
Q (2024, 2 marks): A person of mass 60 kg stands in an elevator. The elevator accelerates upward at 2 m/s^2. What is the apparent weight of the person? (g = 10 m/s^2)
Answer: Given:
m = 60 kg
a = 2 m/s^2 (upward)
g = 10 m/s^2
Apparent weight = Normal force (N)
N = m(g + a)
N = 60(10 + 2)
N = 60 × 12
N = 720 N
Apparent weight = 720 N
Frequently Asked Questions
What is the difference between mass and weight?
Mass is the amount of matter in an object and remains constant everywhere. Weight is the force exerted by gravity on an object and varies with location. Weight = mass × gravitational acceleration.
Can an object have acceleration without changing speed?
Yes. Acceleration is any change in velocity, including change in direction. An object moving in a circle at constant speed has acceleration because its direction is changing.
More Class 11 Physics PYQs
- Current Electricity
- Ray Optics
- Electrostatics
- Moving Charges and Magnetism
- Electromagnetic Induction
- Alternating Current
🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →