Exam 7: Work and Kinetic Energy

The ratio of the kinetic energy of object A to the kinetic energy of the object B is 2: 1. The mass of object A is 2.0 kg and the mass of object B is 4.0 kg. If object A has a speed of 4.0 m/s, what is the speed of object B?

The ratio of kinetic energy of object A to the kinetic energy of object B is 2: 1. Object A is moving with a speed of 6.0 m/s and object B is moving with a speed of 2.0 m/s. If the mass of object A is 4.0 kg then what is the mass of object B?

A weight of 200 N is hung from a spring with a spring constant of 2500 N/m and lowered slowly. How much will the spring stretch?

The kinetic energy of an object increases linearly as the velocity of the object increases.

FIGURE 7-5 -An object is under the influence of a force as represented by the force vs. position graph in Figure 7-5. What is the work done as the object moves from 6 m to 12 m?

The ratio of the mass of object A to the mass of object B is 2: 1 and the ratio of their speeds is 1: 2 in the same order. What is the ratio of their kinetic energies?

You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?

An object hits a wall and bounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial kinetic energy?

A block of mass m is pushed against a spring of spring constant k. The spring is compressed by a distance d, the block is then released. It is launched by the spring along a horizontal frictionless surface with a final speed v. A second block, this one having mass 4m is pushed against the same spring by distance 6d and released. What is the final speed of the block in this case?

An object of mass 10.0 kg is released from the top of an inclined plane which makes an angle of inclination of 30.0° with the horizontal. The object slides along the inclined plane. The questions refer to the instant when the object has traveled through a distance of 2.00 m measured along the slope. The coefficient of kinetic friction between the mass and the surface is 0.200. Use g = 10 m/s². How much work is done by gravity?

FIGURE 7-6 -An object is under the influence of a force as represented by the force vs. position graph as shown in Figure 7-6. What is the work done as it moves from 0 to 10 m?

How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

A 220-kg object is lifted at a constant speed through a height of 42 m by a crane. If the crane takes a total time of 1.8 seconds to lift this object, what is the average power required? Use g = 10 m/s².

A simple pendulum, consisting of a mass m and a string of length L, swings upward, making an angle θ with the vertical. The work done by the tension force is

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

In the SI system of units, power has the same units as

FIGURE 7-1 -Describe the type of spring "constant" needed to produce a constant restoring force like curve (a) in Figure 7-1.

How large a force is required to accelerate a 1600 kg car from rest to a speed of 25 m/s in a distance of 200 m?

A car originally at rest has its speed increased to a value v in a period of 5 seconds. The work performed in this part of the motion is W₁. Over the next 5 seconds the speed of the car is increased to 2v. In the second part of the motion the work performed is W₂. It is correct to say that:

A horizontal force of 40 N pushes an object of mass 5.0 kg up an inclined plane through a distance of 1.6 m measured along the plane. The plane is inclined at an angle of 30° to the horizontal. Neglect friction and use g = 10 m/s². (a) What is the work done by the horizontal force on the object? (b) What is the work done by the net force on the object? (c) What is the work done by the normal force on the object?