large truck and a car,

[question] Question. A large truck and a car, both moving with a velocity of magnitude v, have a head-on collision. If the collision lasts for 1 s (a)Which vehicle experiences greater force of impact ? (b)Which vehicle experiences greater change in momentum ? (c)Which vehicle experiences greater acceleration ? (d)Why is the car likely to suffer more damage than the truck ? [solution] Solution: Let mass of truck $=\mathrm{M} ;$ mass of car $=\mathrm{m} ;$ velocity of truck $=\mathrm{v} ;$ time fo...

Using a horizontal force of 200 N,

[question] Question. Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet ? [question] [solution] Solution: In order to move the cabinet with constant velocity, the net force acting on it should be zero, such that the forces are balanced. This is possible only if the frictional force is 200 N and acts in the direction opposite to the direction of motion of the cabinet....

From a rifle of mass 4 kg,

[question] Question. From a rifle of mass 4 kg, a bullet of mass 50 g is fired with a speed of 35 ms–1 Calculate the recoil speed of the rifle [question] [solution] Solution: Mass of rifle $=4 \mathrm{~kg}$ Let velocity of recoil of rifle $=\mathrm{v}$ Momentum of the rifle $=4 \times \mathrm{v}$ Mass of bullet $=50 \mathrm{~g}=\frac{50}{1000} \mathrm{~kg}=0.05 \mathrm{~kg}$ Velocity of bullet $=35 \mathrm{~ms}^{-1}$ Momentum of bullet $=0.05 \times 35$ Using the law of conservation of momentum,...

Explain, why is it difficult for a fireman to hold a hose pipe

[question] Question. Explain, why is it difficult for a fireman to hold a hose pipe which ejects large amounts of water at high velocity. [/question] [solution] Solution: We can explain the above observation on the basis of law of conservation of momentum. When the system of hose and water is not ejecting any water, its momentum is zero. When the water issues out from the hose with a high velocity, it has momentum in the forward direction. Therefore, in order to conserve momentum, the hose tends...

If action is always equal to the reaction,

[question] Question. If action is always equal to the reaction, explain how a horse can pull a cart. [/question] [solution] Solution: When a horse pulls a cart with a certain force, then the cart pulls the horse with the same force and the system of horse and cart should not move. But, if we analyse the problem carefully, then horse not only applies force on the cart, but also pushes the earth backward with his feet. The earth reacts back to this action of the horse and pushes it in the forward ...

Why do you fall in the forward direction when a moving bus applies brakes

[question] Question. Why do you fall in the forward direction when a moving bus applies brakes to stop and fall backward when it accelerates from rest ? [/question] [solution] Solution: When a moving bus applies brakes, our feet come to rest with the bus. But upper part of our body continues to move forward on account of inertia of motion. That is why we tend to fall in the forward direction. However, when the bus accelerates from rest, lower part of our body moves with the bus. The upper part o...

Explain why some of the leaves may get detached

[question] Question. Explain why some of the leaves may get detached from a tree if we vigorously shake its branch. [question] [solution] Solution: When we shake a branch of a tree vigorously, some of the leaves may get detached on account of inertia of rest of the leaves. The branch comes in motion and the leaves try to be in the position of rest. Therefore, they get detached. [solution]...

In the following example, .

[question] Question. 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. [question] [solution] Solution: The velocity of the football changes four times First time the velocity changes ...

Which of the following has more inertia :

[question] Question. 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 rupees coin and a one-rupee coin ? [/question] [solution] Solution: Mass of a body is the measure of its inertia i.e., more the mass, more is the inertia. Keeping this in mind : (a) Stone has more inertia. (b) Train has more inertia. (c) Five rupees coin has more inertia. [/solution]...