1. Calculate the work done by a 50 N force pushing a cube 0.25 m. 2. Calculate the work done by a 40 N force pushing a 0.5 kg toy 2.3 m. 3. Calculate the force needed to do 500 J of work while pulling a cart a distance of 3.4 m. 4. How much work is it to lift a 25 kg sack of cement vertically 4.3 m? 5. If a small motor does 200 J of work to move a toy 17 m, what force does it exert? 6. A boy pushes his little brother in a box with a force of 500 N for 324 m. How much work is this if the force of friction acting on the sliding box is (a) 100 N, (b) 250. N? 7. A 90.0 kg man pushes on a 5.0 x 106 ton wall for 350 s but it does not move. How much work does he do on the wall? 8. How much power does it take to lift 40.0 N 11.0 m high in 6 s? 9. How much power does it take to lift 50.0 kg 8.0 m high in 4.00 s? 10. You carry a 20. N bag of potatoes up a 5.0 m flight of stairs in 26 seconds. How much work was done? How much power did you used. 11. You push down on a 4.0 N box against the floor for 2 minutes. How much work was done? How much power did you spend? 12. You use 40 J of energy to rise a 250 N object. How far high did you lift it? 13. A 100 watt light bulb runs for 120 seconds. How much energy does it use? Part II Kinetic Energy and Potential Energy. 18. What is the gravitational potential energy of a 70 kg person standing on the roof of a 12-story building relative to (a) the tenth floor, (b) the sixth floor, (c) the first floor? (Each story is 2.80 m high.) 19. A 2 x 104 kg airplane lands, descending a vertical distance of 11.0 km while travelling 120 km measured along the ground. What is the plane's loss of potential energy? 20. Calculate the kinetic energy of a 2 Kilogram cannon ball travelling at: (a) 50 m/s, (b) 45 m/s, (c) 92 m/s. 21. How fast must a 400 kg motorbike be moving to have a kinetic energy of: (a) 1,200 J (b) 1,600 J? 22. A coconut falls out of a tree 10 m above the ground and hits a bystander 2.00 m tall on the top of the head. It bounces back up 1 m before falling to the ground. If the mass of the coconut is 1.5 kg, calculate the potential energy of the coconut relative to the ground at each of the following sites: (a) while it is still in the tree, (b) when it hits the bystander on the head, (c) when it bounces up to its maximum height, (d) when it lands on the ground, (e) when it rolls into a groundhog hole, and falls 2 m to the bottom of the hole. 23. A 50.0 kg bicyclist on a 10.0 kg bicycle speeds up from 5.00 m/s to 10.0 m/s. (a) What was the total kinetic energy before accelerating? (b) What was the total kinetic energy after accelerating? (c) How much work was done to increase the kinetic energy of the bicyclist? 24. How high would you have to lift a 2000 kg car to give it a potential energy of: (a) 4.0 x 103 J, (b) 5.00 x 105 J? 25. Describe the energy transformations that you observe during the motion of a pendulum. Why The Pendulum does not continue oscillating with the same amplitude forever?