Exam 5: Work and Energy

A family goes on vacation for one week, but forgets to turn off an electric fan that consumes electricity at the rate of 200 watts. If the cost of electricity is $0.120/kW-h, how much does it cost to run the fan?

-The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as shown in Figure 5-4. How much work did the squirrel do during that 10. s?

Define power.

Use Figure 5-2 below to answer the following question(s). -In Figure 5-2, showing a pendulum, at what position is the kinetic energy maximum?

Is more work required to increase a car's speed from rest to 30 mph, or from 50 mph to 60 mph?

Car J moves twice as fast as car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K is

My battery charger uses 12. watts. At 6.0 cents per kilowatt-hour, how much does it cost to charge batteries for 24. hours?

A ball is released, from rest, at the left side of the loop-the-loop, at the height, h, as shown in Figure 5-3. -Refer to Figure 5-3. If the radius of the loop is R, what vertical height does the ball rise to, on the other side, neglecting friction?

Use Figure 5-1 below to answer the following question(s). -Which of the graphs above illustrates Hooke's Law?

Assuming negligible friction, what spring constant would be needed by the spring in a "B-B gun" to fire a 10. gram pellet to a height of 100 meters if the spring is initially compressed 10. cm?

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?

A container of water is lifted vertically 3.0 m, then returned to its original position. If the total weight is 30. N, how much work was done?

The resultant force you exert while pressing a key on the keyboard of your new computer, for a 1.0-s period, is plotted in Figure 5-5. Figure 5-5 How much work did you do during this 1-s interval?

A 1.0 kg flashlight falls to the floor. At the point during its fall when it is 0.70 m above the floor, its potential energy exactly equals its kinetic energy. How fast is it moving?

NOTE: The following question(s) refer(s) to the Cyclone, the famous roller coaster ride at Coney Island, shown in the sketch. Assume no friction. -Refer to Figure 5-6. If the roller coaster leaves point Q from rest, how fast is it traveling at point R?

A 10. kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. The spring constant is

Matthew pulls his little sister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 Newtons at an angle of 37.0° upward from the horizontal. If he pulls her a distance of 12.0 m, the work he does is

One horsepower is equal to

To accelerate your car at a constant acceleration, the car's engine must

A cyclist does work at the rate of 500. W while riding. With how much average horizontal force does the wheel push when she is traveling at 10. m/s?