Third Law of Motion

Q.

State the principle of conservation of linear momentum.

Q. Every action has an equal and opposite reaction. Explain.

Q.

KE of a system can be increased without applying any external force to the system.

1. True
2. False

Q. What is recoil velocity?

Q.

Why action and reaction do not cancel out each other?

Q.

APPLICATION OF SECOND LAW OF MOTION :

In high jump events, why the athlete is made to jump on a cushioned bed ?

Q.

The action and the reaction force act on two different bodies. True or false?

1. False

2. True

Q.

A book is kept on the table top and is at rest. The force which acts on the book is

1. gravitational force

2. magnetic force

3. nuclear force

4. electrostatic force

Q. If action is always equal to the reaction, explain how a horse can pull a cart.

Q.

What does action-reaction force mean?

Q. Two blocks of mass 2kg and 4kg are accelerated with same acceleration by a force 10N as shown in figure on a smooth horizontal surface.Then the spring force between the two blocks will be?

Q.

When a carpet is beaten with a stick, dust comes out of it. Explain why this happens? [2 MARKS]

Q.

According to Newton's third law of motion, the action and reaction always act on:

1. Different bodies.

2. The same body.

3. Same direction.

4. The same body and in the same direction.

Q.

According to the third law of motion, action and reaction

1. always act on the same body

2. always act on different bodies in opposite directions

3. have same magnitude and directions

4. act on either body at normal to each other

Q.

Give two examples from everyday life where the Newtons third law of motion comes into play?

Q.

Explain how inertia is used to dust a floormat and to remove water drops from a wet cloth. [3 MARKS]

Q.

One gram force is equal to 10 N

1. True
2. False

Q.

The magnitude of force that the earth exerts on the moon is the same as that of the force that the moon exerts on the Earth.

1. True

2. False

Q.

Give information about commonly used gadgets or devices which are based on the principles of newtons laws of motion.

Q.

If an external force acts on a system, can momentum be conserved?

Q. Action and reaction are a pair of force which acts on different bodies.

1. True
2. False

Q.

Use Newton's laws of motion to explain the flying of an aeroplane ?

Q. State of motion or rest depends on the observer.

1. True
2. False

Q.

The action and the reaction force act on two different bodies.

1. True

2. False

Q.

According to Newton's third law of motion- "Every action has an equal and opposite reaction".

1. True

2. False

Q. Newton’s third law of motion states that for every action, there is an equal and opposite reaction. Which of the following statements can be inferred from the above-mentioned law of motion?
Statement 1: For every interaction, there is a pair of forces acting on the two interacting objects.
Statement 2: The magnitude of the force on the first object equals the magnitude of the force on the second object.
Statement 3: Forces always come in pairs - equal and opposite action-reaction force pairs.
Statement 4: Action and its reaction act on the same bodies.
Statement 5: Action and its reaction act on two different bodies.

1. All statements except 4 can be inferred from $3^{rd}$ law of motion
2. Only statement 1 can be inferred from $3^{rd}$ law of motion
3. All statements except 5 can be inferred from $3^{rd}$ law of motion
4. All statements can be inferred from $3^{rd}$ law of motion

Q.

Action and reaction force are equal in magnitude but opposite in direction.

1. True

2. False

Q. Question 5
A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tons (Hint: 1 metric ton = 1000 kg).

Q.

The flight of a bird is associated with which Newton's law of motion. Give a suitable example to justify your answer.

Q. A machine gun fires n bullets per second with speed u , and mass of each bullet is m . If bullets hit a wall and rebounds with same speed , then force acting on wall is