26. (b) How much work is required to stretch the cord by this much? 27. A spring with a force Constant of 5.20 N/mhas a relaxed length of 2.45 m. When a mass is attachedtO the end the spring and allowed to come to rest, the vertical length of the spring is 3.57 m. Calculate the elastic potential energy stored in the spring. 28. The staples inside a stapler kept in place by a spring with a relaxed length of 0.115m. Ifthe spring constant is 51.0 N/m, how much elastic potential energy is store in the spring when its length is O. 150 m? 29. A 6.0 kgmetal ball moving at 4.0 mis hits a 6.0 kg ball ofputty at rest and sticks to it. The two go on at 2.0 ws (a) What is the kinetic energy of the metal ball before it hits? (b) What is the kinetic energy of the metal ball after it hits? (c) What is the kinetic energy of the putty ball aner being hit? (d) How much energy does the metal ball lose in the collision? (e) How much kinetic energy does theputty ball gain in the collision? (t) What happened to the rest of the energy? Conservation Of Energy 1. A 10. kgballis thrown into the air. It is going3.&.m/s when thrown. How much potential energy will ithaveat the top? A 4768-kg roller coaster train full of riders approaches the loading dockat a speed of 17.1 mis. Itis abruptly decelerated to a speed of 2.20 IW's over a distance of 13.6 m. Determine the magnitude of the retarding force which acts upon the roller coaster cars. 3. A 4.00 kgballis on a 5.00m ledge. Ifitis pushed off the ledge, how much kinetic ener will it have just before hitting the ground? 4. A 25 kg ball is thrown into the air. When thrown itis going 10. Ws. Calculate how high it travels. 5. A 3.0 kgrocksits on a 0.80 meter ledge. If itis pushed off, how fast will it be going at the bottom? 6. A catcher's mitt recoils a distance of 12.9 cm in bringing a .142-gram baseball to a stoi. Ifthe appliedforce is 588 N, then what was the speed Of the baseball at the moment Of contact-with the mitt? 7. An unknown force is applied to a 12 kg mass. The force acts at an angle of 30.0 degrees above the horizontal. Determine the force acting if the force acts foy a horizontal displacement of 22 meters and increases the 12 kg mass's speed from 11 IL's to 26 m/s. A physics teacher exerts a force upon a 3.29-kg pile of snow to both lift it and set it into motion. The snow leaves the shovel with a speed of 2.94 mis at a height of 0.562 m. Determine the work done upon the pile Of snow. 9. A 250.-gram cart starts and rolis down an inclined plane from a height of 0.541 m. at a height of 0.127 m above the bottom of the incline. 10. A 4357-kg roller coaster car starts from rest at the top Of a 36.5-m high track. Determine the speed of the car at the top Of a loop that is 10.8 m high. 11. While on the moon, the Apollo astronauts enjoyed the effects of a small gravity. IfNeil Armstrong jumped up On the moon with an initial speed Of 1.51 m/s to a height f 0.700m, what amount of graVitational acceleration did he experience? Work, Energy and Power page 4