Physics 1-L Conservation of Energy

Problems - Show your work. Name______Period______

1. A 65 kg diver is poised at the edge of a 15 m platform. (a) Calculate the diver's gravitational potential energy relative to the pool. (b) He dives from the platform. How much kinetic energy will he have when he hits the water? (c) How fast is he going when he hits the water?

2. A 2.4 kg ball is thrown straight up with a speed of 35 m/s. (a) What is its initial kinetic energy? (b) Find the maximum height the ball will attain.

3. A 1250 kg car is moving along a level road at 63 km/h. (a) How much kinetic energy does the car have? (b) If the engine is turned off at the bottom of the hill, to what height will the car coast, neglecting friction?

4. A 1,300 kg car starts at rest and rolls down a hill from a height of 10 m. (a) How much kinetic energy does the car have at the bottom of the hill? (b) How fast is it traveling? (c) The car then collides with a light spring-loaded guardrail. Find the maximum distance the spring is compressed. Assume a spring constant of 1.0 x 106 N/m. 5. An archer pulls her bow string back 0.40 m by exerting a force that increases uniformly from zero to 230 N. (a) What is the equivalent spring constant of the bow? (b) What is the average force used in pulling the bow string? (c) How much work is done in pulling the bow string?

6. The spring constant of a spring in a 0.4 kg child's toy is 550 N/m. (a) How much elastic potential energy is in the spring if it compressed a distance of 1.2 cm? (b) If all of the spring energy is converted into kinetic energy, how fast will the toy be moving after the spring is released?

7. A force of 22 N is exerted horizontally on an 18 kg box to move it 7.6 m across the floor. If the box was initially at rest and is now moving at 3.2 m/s, calculate (a) the work done, (b) the final kinetic energy of the box, and (c) the energy converted to thermal energy (i.e. heat) due to friction.

8. A 72 kg pole vaulter running at 8.4 m/s completes a vault. If all his kinetic energy is transformed into gravitational potential energy, what is the maximum height of the bar?

9. A 0.10 kg arrow is pulled back 30 cm against a bowstring. If the force constant of the bow and string is 1250 N/m, (a) How much elastic potential energy is stored in the bow? (b) At what speed will the arrow leave the bow?

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1. a. 9555 J b. 9555 J c. 17.1 m/s 2. a. 1470 J b. 62.5 m 3. a. 191kJ b. 15.6 m 4. a. 127.4 kJ b. 14 m/s c. 0.505 m

5 5. .a. 575 N/m b. 115 N c. 46J 6.a. 0.0396 J b. 0.445 m/s 7. a. 167.2 J b. 92.16 J c. 75.04 J 8. 3.6 m 9. a. 56.3 J b. 33.5 m/s