Question

4. State Newton's second law of motion

5. Newton's first law of motion is also called the law of inertia, why?
Clarify your answer.
6. An electric fan continues in its motion even after the switch is put
off, why?
7. Dust particles fall down when a carpet or a piece of cloth is beaten
by a stick, why?
8. While swimming a person pushes water backward, why?
9. A cricket player catches the ball leaning towards to the ground, why?
10. Prove that s = ut +1/2 at?
11. State Newton's third law of motion and write any thre
applications of it.
12. Prove that v2 = u’ + 2as.
ience. Grade - 9​

Answer 1

1. It states that the net external force acting on a body is directly proportional to the rate of charge in its momentum.
2. Interia is the tendency of an object to resist a change in motion.
3. The electric fan continues to rotate for some time after the current is switched off due to the rotational interia force.
4. An object interia tends to resist any change in its state of rest or motion.If a carpet is beaten with a stick then the carpet begins to move.But the particles of dust are trying yo resist their state of rest.
5. A person pushes the water with his hands in the backward direction while swimming .In turn water in the pool pushes him forward due to the reaction force .When a carpet with a stick dust comes out.
6. As it is in earth's atmosphere the ball experiences an external force from the wind and keeps on slowing down.The idea to lower the hands while catching the ball is to save it from pain or injury.The more the ball remains in air the lesser force it puts as it falls in the hands of the fielder.
7. acceleration=change in velocity/time acceleration=final velocity-inital velocity/time. =acceleration=v-u/t a=v-u/t at=v-u at+u=v v=at+u