Force and Laws of Motion - NCERT Solutions (Part 1) | Class 9 Physics

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✅ In this video,

✔️ Class: 9
✔️ Subject: Physics
✔️ Chapter: Force and Laws of Motion
✔️ Topic Name: NCERT Solutions (Part 1)
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00:00 Introduction
00:03 NCERT Solutions Question 1
05:33 Question 2
06:32 Question 3
16:40 Question 4
19:34 Website Overview
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NCERT Solutions
Question 1. Which of the following has more inertia:
(a) a rubber ball and a stone of the same size?
(b) a bicycle and a train?
(c) a five rupee coin and a one-rupee coin?
Answer. Mass is a measure of the inertia of an object. If an object has more mass, it has more inertia.
- A stone has more inertia (than a rubber ball of the same size) because it has more mass than a rubber ball of the same size.
- A train has more inertia (than a bicycle) because it has more mass than a bicycle.
- A five-rupee coin has more inertia (than a one rupee coin) because it has more mass than a one rupee coin.

Question 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.
Answer.
I. the velocity of football changes for the 1st time when a football player kicks the football to another player of his team. The agent supplying the force in this case is the kick applied by the player.
II. the velocity of football changes for the 2nd time when the another player of the same team kicks the football towards goal. Here the force is supplied by the kick of another player.
III. the velocity of football changed the 3rd time when the goalkeeper of opposite team collects the football (or stops the football). In this case the force is applied by the hands of goalkeeper.
IV. The velocity of football changes for the 4th time when the goalkeeper kicks the stationary football towards a player of his own team. Here, the force is supplied by the kick of goalkeeper.
Thus, the velocity of football changes four times. .