# Laws of Motion Exe-3B Short Answer Physics Class-9 ICSE Selina Publishers

Laws of Motion Exe-3B Newton’s First Law Inertia Short Answer Type for Class-9 ICSE Concise Physics. There is the solutions of short Answer type Questions of your latest textbook which is applicable in 2023-24 academic sessionVisit official Website CISCE for detail information about ICSE Board Class-9.

## Laws of Motion Exe-3B Newton’s First Law Inertia Short Answer

(ICSE Class – 9 Physics Concise Selina Publishers)

 Board ICSE Class 9 Subject Physics Writer / Publication Concise selina Publishers Chapter-3 Laws of Motion Exe – 3B Newton’s First Law Inertia Topics Solution of Exe-3(B) Short Answer Type Academic Session 2023-2024

### Exe-3B Newton’s First Law Inertia Short Answer Type

Ch-3 Laws of Motion Physics Class-9 ICSE Concise

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#### Question 1. A ball moving on a table eventually stops. Explain the reason.

The force of friction between the table and the ball opposes the motion of the ball.

#### Question 2. What is meant by the term inertia?

The property of an object by virtue of which it neither changes its state nor tends to change the state is called inertia.

#### Question 3. Give two examples to show that greater the mass, greater is the inertia of the body.

Examples to show that greater the mass, greater is the inertia of the body are as shown below:

(i) If you want to start a car by pushing it, you find that it takes a very large force to overcome its inertia. On the other hand, only a small force is needed to start a child’s express wagon. The difference between the car and express wagon is the difference in mass. The car has a large mass, whereas the wagon has a small one.

(ii) A cricket ball is more massive than a tennis ball. The cricket ball acquires a much smaller velocity than a tennis ball when the two balls are pushed with equal force for the same time.

#### Question 4. ‘More the mass, the more difficult it is to move the body from rest’. Explain this statement by giving an example.

It is difficult, i.e. a larger force is required to set a loaded trolley (which has more mass) in motion than an unloaded trolley (which has less mass).

#### Question 5. Two equal and opposite forces act on a stationary body. Will the body move? Give a reason to your answer.

No, the body will not move because the net force acting on it is zero. Hence, it will remain stationary due to inertia of rest.

#### Question 6. Two equal and opposite forces act on a moving object. How is its motion affected? Give reason.

The motion remains unaffected because the net force acting on it is zero.

#### Question 7. Why does a person fall when he jumps out from a moving train ?

If a person jumps out of a moving train and tries to stop immediately, he falls due to inertia of motion. This is because his body tends to move forward with the velocity of the train  while his feet are stationary.

(Laws of Motion Exe-3B Short Class-9 ICSE)

#### Question 8. Why does a coin, placed on a card, drop into the tumbler when the card is rapidly flicked with a finger?

The reason is that when the card is flicked, a momentary force acts on the card, so it moves away. However, the coin kept on it does not share the motion at once and it remains stationary at its place due to the inertia of rest. The coin then falls down into the tumbler due to the pull of gravity.

#### Question 9. Why does  a ball is thrown vertically upwards from a moving train it comes back to the thrower’s hand.

The reason is that when the ball is thrown, the ball is in motion along with the person and train. Due to the inertia of motion, during the time the ball remains in air, the person and ball move ahead by the same distance. This makes the ball fall back into the thrower’s hand.