Exam 7: Work and Kinetic Energy

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 4 m to 6 m?

Power is a vector quantity.

Work is a vector quantity.

An object of mass 10.0 kg is initially at rest. A 100 N force causes it to move horizontally through a distance of 6.00 m. What is the change in the kinetic energy of this object?

4.0 J of work are performed in stretching a spring with a spring constant of 2500 N/m. How much is the spring stretched?

Compared to yesterday, you did 3 times the work in one-third the time. To do so, your power output must have been

An object of mass m moving in a certain direction has a kinetic energy of 4.0 J. It hits a wall and comes back with half its original kinetic energy. If the speed of the object on return is 2.0 m/s, what is the mass of the object?

What is the horsepower needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s in 4.00 seconds?

Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do.

Daisy raises 10.Kg to a height of 2.5 meters in 2.0 seconds. (a) How much work did she do? (b) How much power was expended? (c) If she raises it in 1.0 s rather than 2.0 s, how do the work and power change?

FIGURE 7-1 -Which of the graphs in Figure 7-1 represents a spring which gets less stiff the more it is stretched?

A 4.00-kg mass is attached to a spring hanging vertically and hangs at rest in the equilibrium position. The spring constant of the spring is 1.00 N/cm. The mass is pulled downward 2.00 cm and released. What is the speed of the mass when it is 1.00 cm above the point from which it was released?

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 10 to 15 m?

An object of 1.0 kg mass is pulled up an inclined plane by a constant force of 10 N that causes a displacement of 0.50 m. The angle of inclination with the horizontal is 30°. Neglect friction and use g = 10 m/s². What is the work done by the net force on the object along the inclined plane?

Work done by a force on an object can be a positive or a negative quantity.

A constant force is applied to an object that causes a certain displacement. If the angle between the force and the displacement is 135°, the work done by this force is

A boy throws a ball to another boy who throws it back with half the original speed. What is the ratio of the final kinetic energy to the initial kinetic energy of the ball?

I left five 100. watt bulbs burning in my basement for two weeks. If electricity costs me 10.¢/kw-h, how much did the electricity cost (to the nearest dollar) to leave these bulbs on and how many Joules of electrical energy did they consume?

If the work done to stretch a spring by 4.0 cm is 6.0 J, what is the spring constant?

A 1.0-kg object moving in a certain direction has a kinetic energy of 2.0 J. It hits a wall and comes back with half its original speed. What is the kinetic energy of this object at this point?