Exam 7: Kinetic Energy and Work

An escalator is used to move 20 people (60 kg each) per minute from the first floor of a department store to the second floor, 5 m above. The power required is approximately:

An object moves in a circle at constant speed. The work done by the centripetal force is zero because:

A kilowatt hour is a unit of:

A particle starts from rest at time t = 0 and moves along the x axis. If the net force on it is proportional to t, its kinetic energy is proportional to:

The work done by gravity during the descent of a projectile is:

A sledge (including load) weighs 5000 N. It is pulled on level snow by a dog team exerting a horizontal force on it. The coefficient of kinetic friction between sledge and snow is 0.05. How much work is done by the dog team pulling the sledge 1000 m at constant speed?

A line drive to the shortstop is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s. The work done on the object during one revolution is:

A 2-kg block is attached to a horizontal ideal spring with a spring constant of 200 N/m. When the spring has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring?

The velocity of a particle moving along the x axis changes from v_i to v_f. For which values of v_i and v_f is the total work done on the particle positive?

Which of the following five units represents a quantity that is NOT the same type as the other four?

A baseball is hit high into the upper bleachers of left field. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

At time t = 0 a 2-kg particle has a velocity of (4 m/s) - (3 m/s). At t = 3 s its velocity is (2 m/s) + (3 m/s). During this time the work done on it was:

A force = (4.1 N) + (2.6 N) - (4.7 N) acts on a mass of 2.3 kg as it moves in the x direction at a speed of 7.2 m/s. What is the rate at which the force is doing work?

Which of the following bodies has the largest kinetic energy?

The plot shows the force on an object as it moves from x = 0 m to x = 20 m. How much work is done on the object?

A crate is initially at rest on a horizontal frictionless table. A constant horizontal force F is applied. Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Power has the dimensions of:

When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx², where a and b are constants. The work done in stretching this rubber band from x = 0 to x = L is:

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s²?