H C Verma Solutions for Chapter: Newton's Laws of Motion, Exercise 1: QUESTIONS FOR SHORT ANSWER

Suppose you are running fast in a field when you suddenly find a snake in front of you. You stop quickly. Which force is responsible for your deceleration?

If you jump barefooted on a hard surface, your legs get injured. But they are not injured if you jump on a soft surface like a sand or pillow. Explain.

According to Newton's third law, each team pulls the opposite team with equal force in a tug of war. Why then, one team wins and the other loses?

A spy jumps from an aeroplane with his parachute. The spy accelerates downward for some time when the parachute opens. The acceleration is suddenly checked and the spy slowly falls on the ground. Explain the action of a parachute in checking the acceleration.

Consider a book lying on a table. The weight of the book and the normal force by the table on the book are equal in magnitude and opposite in direction. Is this an example of Newton's third law?

Two blocks of unequal masses are tied by a spring. The blocks are pulled stretching the spring slightly and the system is released on a frictionless horizontal platform. Are the forces due to the spring on the two blocks equal and opposite? If yes, is it an example of Newton's third law?

When a train starts, the head of a standing passenger seems to be pushed backwards. Analyse the situation from the ground frame. Does it really go backwards? Coming back to the train frame, how do you explain the backward movement of the head on the basis of Newton's laws?

A plumb bob is hung from the ceiling of a train compartment. If the train moves with an acceleration $a$ along a straight horizontal track, the string supporting the bob makes an angle ${\tan }^{-1}\left(\frac{a}{g}\right)$ with the normal to the ceiling. Suppose the train moves on an inclined straight track with a uniform velocity. If the angle of incline is ${\tan }^{-1}\left(\frac{a}{g}\right)$ the string again makes the same angle with the normal to the ceiling. Can a person sitting inside the compartment tell by looking at the plumb line whether the train is accelerated on a horizontal straight track or it is going on an incline? If yes, how? If no, suggest a method to do so.