Work and Energy Physics - Work and Energy

______ of a two particle system depends only on the separation between the two particles. The most appropriate choice for the blank space in the above sentence is:

1. Kinetic energy.
2. Total mechanical energy.
3. Potential energy.
4. Total energy.

The negative of the work done by the conservative internal forces on a system equals the change in:

1. T​​​​​otal energy.
2. Kinetic energy.
3. Potential energy.
4. None of these.

The work done by all the forces (external and internal) on a system equals the change in:

1. Total energy.
2. Kinetic energy.
3. Potential energy.
4. None of these.

A box is pushed through 4.0m across a floor offering 100N resistance. How much work is done by the resisting force?

A projectile is fired from the top of a 40m high cliff with an initial speed of 50m/s at an unknown angle. Find its speed when it hits the ground.

Consider the situation shown in figure. Initially the spring is unstretched when the system is released from rest. Assuming no friction in the pulley, find the maximum elongation of the spring.

An unruly demonstrator lifts a stone of mass 200g from the ground and throws it at his opponent. At the time of projection, the stone is 150cm above the ground and has a speed of 3.00m/s. Calculate the work done by the demonstrator during the process. If it takes one second for the demonstrator to lift the stone and throw, what horsepower does he use?

A force F = a + bx acts on a particle in the x-direction, where a and b are constants. Find the work done by this force during a displacement from x = 0 to x = d.

The 200m free style women's swimming gold medal at Seol Olympic 1988 went to Heike Friendrich of East Germany when she set a new Olympic record of 1 minute and 57.56 seconds. Assume that she covered most of the distance with a uniform speed and had to exert 460W to maintain her speed. Calculate the average force of resistance offered by the water during the swim.

Consider the situation of the previous question from a frame moving with a speed v0 parallel to the initial velocity of the block.

1. What are the initial and final kinetic energies?
2. What is the work done by the kinetic friction?

Can kinetic energy of a system be increased without applying any external force on the system?

A particle is released from the top of an incline of height h. Does the kinetic energy of the particle at the bottom of the incline depend on the angle of incline? Do you need any more information to answer this question in Yes or No?

A simple pendulum consists of a 50cm long string connected to a 100g ball. The ball is pulled aside so that the string makes an angle of 37° with the vertical and is then released. Find the tension in the string when the bob is at its lowest position.

When you push your bicycle up on an incline the potential energy of the bicyle and yourself increases. Where does this energy come from?

In one of the exercises to strengthen the wrist and fingers, a person squeezes and releases a soft rubber ball. Is the work done on the ball positive, negative or zero during compression? During expansion?

In tug of war, the team that exerts a larger tangential force on the ground wins. Consider the period in which a team is dragging the opposite team by applying a larger tangential force on the ground. List which of the following works are positive, which are negative and which are zero?

1. Work by the winning team on the losing team.
2. Work by the losing team on the winning team.
3. Work by the ground on the winning team.
4. Work by the ground on the losing team.
5. Total external work on the two teams.

Can static friction do nonzero work on an object? If yes, give an example. If no, give reason.

Can the work by kinetic friction on an object be positive? Zero?

A 250g block slides on a rough horizontal table. Find the work done by the frictional force in bringing the block to rest if it is initially moving at a speed of 40cm/s. If the friction coefficient between the table and the block is 0.1, how far does the block move before coming to rest?