PHYSICS WORKSHEET: WORK & ENERGY
1. A 1.20 x 103 kg block starting from rest is accelerated by a 2.20 x 103 N force for a distance of 50.0 meters along a horizontal frictionless surface. (a) What is the final velocity of the mass? (b) How much work was done on the mass?
2. A stock boy is told to put boxes of mass 5.0 kg on shelves that are 1.5 meters above the floor. The young man finds that he can do this at a rate of 4.0 per minute. (a) How much work will he do in 15 minutes? (b) What is his power for this job?
3. A horse pulls a carriage filled with people around a circular park road of radius 0.50 km. The horse exerts an average force of 8.0 x 102 How much work does the horse do in a round trip? (b) If it takes 12 minutes to circle the park, what is the horse's power output?
4. A girl starts from home a pulls her wagon around the block (a distance of 700.0 meters). The wagon weighs 90.0 N and the handle makes an angle of 40.0o with the road. If he pulls with an average force of 75.0 N, how much work does he do?
5. A spring has a spring constant of 248 N/m. Find the force required to (a) stretch the spring by 3.00 cm, and (b) compress the spring by the same amount.
6. A 170 N force is necessary to compress a spring a distance of 40.0 cm. (a) What is the spring constant? (b) What is the elastic potential energy stored in the spring? (c) What energy would be stored in the spring if it were compressed 80.0 cm?
7. A spring has spring constant k = 380 N/m. How much must this spring be compressed to store 60.0 Joules of energy?
8. A physics book weighing 20.0 N is dropped from a position 2.00 meters above the floor. (a) What is the potential energy of the book before it is dropped? (b) What is the kinetic energy of the book when it is 1.00 meter from the floor? (c) What is the speed of the book the instant before it reaches the floor?
9. A ball of mass 0.50 kg is rolling across a table top with a speed of 5.0 m/s. When the ball reaches the edge of the table, it rolls down an incline onto the floor 1.0 meter below (w/o bouncing).
What is the speed of the ball when it reaches the floor?
10. A hot-wheels car of mass 0.025 kg is traveling on a horizontal track with a velocity of 5.0 m/s. If the track suddenly turns upward, how high up the track will the car travel?
11. Figure 1 shows a 1.00 kg object ready to start sliding downward on a frictionless track. Compute the velocity of the object at points B, and C.
12. Some children go tobogganing on an icy hill. They start from rest at the top of the hill as shown in the diagram. The toboggan and children have a combined mass of 9.0 x 101 kg. If friction is small enough to be ignored, determine:
(a) The total mechanical energy of the toboggan at A.
(b) The speed of the toboggan at B.
(c) The speed of the toboggan at C.
13. A boy fires a 60.0 g pebble with his slingshot. The pebble leaves the slingshot at 35 m/s. (a) How high above the slingshot will the pebble rise if it is fired straight up? (b) If the pebble is fired so that it goes in an arc and has a speed of 10.0 m/s at its maximum height, what will the maximum height be? (c) At what speed would an 80.0 g pebble have to be fired to reach the same height as the pebble in (a)? Assume that the 80.0 g pebble is also fired straight up.
14. A rodeo rider is riding a bucking bronco when he is thrown off. At the instant he leaves the horse he is located 1.6 m above the ground and is moving straight up at 4.0 m/s. (a) What maximum height above the ground does the rider reach? (b) At what speed will the rider hit the ground?
15. A spring constant for the spring in a dart gun is 1250 N/m. When the gun is cocked, the spring is compressed by 8.0 centimeters. (a) What is the kinetic energy of a 2.40 gram dart when it leaves the gun horizontally? (b) What is the speed of the dart as it leaves the gun?
16. An 8.0 kg lab cart is held against a horizontal spring, compressing it 50.0 cm. The spring constant is 6.00 x 102 N/m. After the cart is released, it travels along a horizontal table until it encounters an upward incline. At what height above the table will the cart come to a rest?
17. Wile- E - Coyote spied the road-runner asleep in a nest at the top of a smooth, steep hill that is 30.0 meters high. Unable to scale the hill, the coyote puts on a pair of frictionless roller skates and a a spring loaded backpack with 1.10 x 104 J of stored energy. Standing with his back to a cliff and facing the hill, the coyote releases the energy in the backpack. Does the coyote reach the top of the hill? Neglect friction.
18. (a) What is the kinetic energy of a 4.0 kg mass moving at 5.0 m/s? (b) If the mass was accelerated to this speed from rest by a force of 20.0 N, over how long a distance did it act?
19. As a 2.0 kg block of wood slides along a floor, its speed decreases from 4.0 m/s to 1.0 m/s. (a) How much kinetic energy does is lose? (b) How much work does the frictional resistance of the floor do upon the block? (c) If the reduction in speed takes place over a distance of 10.0 m, what is the force of friction on the block?
20. The speed of an automobile of mass 1.60 x 103 kg increases uniformly from 20.0 m/s to 30.0 m/s. (a) What is it's increase in Kinetic Energy? (b) If the acceleration is uniform over a distance of 50.0 m, what force is accelerating this automobile?