Class 9 Science Chapter 8 – Force and Laws of Motion Intext Questions and Answers | NCERT Solutions

Class 9 Science Chapter 8 – Force and Laws of Motion Intext Questions and NCERT Solutions|

Class 9 Science Chapter 8 Force and Laws of Motion me aap Newton ke three laws, momentum, force ke effects aur real-life examples ke baare me padhte hain. Is post me hum NCERT textbook ke sabhi Intext Questions and Answers ko simple, easy language me explain kar rahe hain, taaki aap exam ke liye concepts ko jaldi samajh sako aur revise kar saken. Yah solutions Class 9 students ke liye bilkul accurate, board-oriented aur exam-ready hain.

 

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FORCE AND LAWS OF MOTION
 
INTEXT QUESTION ANSWER

Ques 1:- Which of the following has more inertia:

(a) a rubber ball and a stone of the same size?

ANS :-  Inertia is the measure of the mass of the body.

More mass =  More Inertia

Less mass = Less Inertia

(a) Mass of a stone is more than the mass of a rubber ball for the same size.

Hence, inertia of the stone is greater than that of a rubber ball.

(b) a bicycle and a train?

(b) Mass of a train is more than the mass of a bicycle.

Hence, inertia of the train is greater than that of the bicycle.

 

(c) a five rupees coin and a one-rupee coin?

(c) Mass of a five rupee coin is more than that of a one-rupee coin.

Hence, inertia of the five rupee coin is greater than that of the one-rupee coin. 

Ques 2:- In the following example, try to identify the number of times the velocity of the ball changes: “A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team”. Also identify the agent supplying the force in each case. 

ANS :- Velocity of ball can change if

-- Speed of the ball changes

-- Direction of the ball changes 

Case 1 :-

"football player kicks a football to another player of his team' In this case, the first football player changes the direction of the ball as he kicks it Hence, velocity changes.

The force is applied by the first football player.

Case 2 :-

"another player of his team who kicks the football towards the goal " In this case the second football player changes the direction of the ball as he kicks it towards the goal. Hence velocity changes.

The force is applied by the second football player.

Case 3 :-

"The goalkeeper of the opposite team collects the football".

Goalkeeper collects the football means the goalkeeper stops the football. Since the speed of the ball changes , hence velocity changes

 The force is applied by the goalkeeper in a direction opposite to that of motion.

Case 4 :-

"and kicks it towards a player of his own team"

In this case, the goalkeeper changes the speed of the ball from zero to some speed

Since the speed of the ball changes , hence velocity changes

The force is applied by the goalkeeper

Hence, in the given example, the velocity of the ball changes four times.

Ques 3:- Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.

ANS :- When the branch of a tree is shaken vigorously, it comes in motion while the leaves tend to remain at rest due to inertia of rest. Therefore some of the leaves get detached from the branch of a tree. 

Ques 4: - Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?

ANS: - In a moving bus our speed is equal to the speed of bus. When the bus stops suddenly the lower part of the body which is in contact with the bus comes to rest But the upper part is still in motion due to inertia of motion. So, the passenger is pushed forward. Similarly, when the bus accelerates from rest, the feet come into motion while upper part of the body remains at rest due to inertia of rest. So, the passenger is fall backward.