Physics: Laws of Motion Class 11 MCQ

Understanding the laws of motion is fundamental to grasping the behavior of objects in our universe. Sir Isaac Newton, in the 17th century, laid down three foundational laws that describe the relationship between a body and the forces acting upon it, and the body’s motion in response to those forces. Here are 15 multiple-choice questions that test your knowledge of these essential laws:

1. Newton’s first law of motion is also known as:

a) Law of Inertia
b) Law of Acceleration
c) Law of Interaction
d) Law of Gravitation

Answer:

a) Law of Inertia

Explanation:

Newton’s first law states that an object will remain at rest or move in a straight line at a constant speed unless acted upon by an external force. This property is called inertia.

2. The quantity which measures an object’s resistance to change in its velocity is:

a) Speed
b) Momentum
c) Inertia
d) Acceleration

Answer:

c) Inertia

Explanation:

Inertia is the inherent property of a body that resists changes in its state of motion.

3. If a net force acting on an object is zero, then the object:

a) Must be at rest
b) Can be moving at a constant velocity
c) Will eventually come to rest
d) Cannot be moving

Answer:

b) Can be moving at a constant velocity

Explanation:

According to Newton’s first law, an object can either be at rest or move at a constant velocity when no net force acts on it.

4. Newton’s third law of motion states:

a) Every action has an equal and opposite reaction
b) Force equals mass times acceleration
c) Objects in motion stay in motion
d) Force is directly proportional to displacement

Answer:

a) Every action has an equal and opposite reaction

Explanation:

This means that for every force, there is a force of equal magnitude but in the opposite direction acting on another body.

5. If you push a wall with a force of 10N, the wall pushes back with:

a) No force
b) 5N force
c) 10N force
d) 20N force

Answer:

c) 10N force

Explanation:

According to Newton’s third law, every action has an equal and opposite reaction.

6. Which of the following is the correct expression for Newton’s second law?

a) F = ma
b) F = mv
c) a = Fm
d) v = Fa

Answer:

a) F = ma

Explanation:

Newton’s second law states that the force acting on an object is equal to the mass of that object times its acceleration.

7. A body of mass 10 kg is moving with a constant velocity of 10 m/s. The net force acting on the body is:

a) 0 N
b) 10 N
c) 100 N
d) 1 N

Answer:

a) 0 N

Explanation:

If the velocity is constant, it means there’s no acceleration, and hence no net force acting on the body.

8. The unit of force in SI units is:

a) Joule
b) Pascal
c) Newton
d) Watt

Answer:

c) Newton

Explanation:

In the SI system, the unit of force is Newton (N).

9. When an object is in free fall, the only force acting on it is:

a) Friction
b) Applied force
c) Normal force
d) Gravitational force

Answer:

d) Gravitational force

Explanation:

In free fall, the only significant force acting on the object is the gravitational pull from the Earth.

10. An object moving in a circle at constant speed:

a) Has a constant velocity
b) Is not accelerated
c) Has a changing velocity
d) Has no net force acting on it

Answer:

c) Has a changing velocity

Explanation:

Even if the speed is constant, the direction is changing. Hence, velocity (which has both magnitude and direction) is changing.

11. An object of mass 5 kg is accelerating at 2 m/s^2. The force exerted on the object is:

a) 2.5 N
b) 7.5 N
c) 10 N
d) 25 N

Answer:

d) 25 N

Explanation:

Using Newton’s second law, F = ma, the force is 5 kg x 2 m/s^2 = 10 N.

12. Which of these is NOT a contact force?

a) Frictional force
b) Tension force
c) Magnetic force
d) Normal force

Answer:

c) Magnetic force

Explanation:

Magnetic force can act over a distance without direct contact, making it a non-contact force.

13. A car moving on a straight road comes to a stop after a certain distance, when its engine is switched off. This is due to:

a) The driver pushing the brake pedal
b) The natural force of attraction between the tires and the road
c) The frictional force between the car tires and the road
d) The car running out of fuel

Answer:

c) The frictional force between the car tires and the road

Explanation:

The frictional force acts opposite to the direction of motion, slowing the car down and eventually stopping it.

14. A book is resting on a table. The reaction to the Earth’s gravitational force acting on the book is:

a) The gravitational force of the book on the Earth
b) The normal force exerted by the table on the book
c) The frictional force between the book and the table
d) None of the above

Answer:

a) The gravitational force of the book on the Earth

Explanation:

According to Newton’s third law, every action has an equal and opposite reaction. The Earth pulls the book with gravitational force, and the book also pulls the Earth with an equal and opposite gravitational force.

15. In the absence of an external force, a moving object will:

a) Slow down and come to a stop
b) Change direction and move in a circular path
c) Move with a uniformly increasing velocity
d) Continue moving at a constant velocity

Answer:

d) Continue moving at a constant velocity

Explanation:

According to Newton’s first law (Law of Inertia), in the absence of an external force, an object will continue in its state of motion, which can be rest or uniform motion in a straight line.

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