1) A block of ice is dragged along the ground as shown. There is no friction F,= 120 N a) Label the forces acting on the box b) How much work is done on the box? 60 120 kg - 13 m c) What is the increase in kinetic energy? (ans. 780 J) d) How fast is the block moving at the end of the 13 m? (ans. 3.6 m/s ) What is the normal force acting on the block? (ans. 1070 N) f) How much energy would be lost to friction if the coefficient between the block and the ground is u= 0.02? (ans. -278 J) g) How fast would the box be moving in question (f)? 2) Determine how the energy changes in each description. a) A cannon ball has 1200 J of kinetic energy. What is the kinetic energy if the speed of the cannon ball was three times faster? b) A flower pot has 250 J of potential energy. What is the potential energy if the pot is moved to half its original height? c) A flying bee has 12 J of kinetic energy. What is the speed of the bee at half its original speed? d) A frictionless roller coaster has 15000 joules of mechanical energy when it is moving at 12 m/s at a height of 20 m. What is its mechanical energy when the coaster drops to 10 m? 3) A skater starts from rest at height A which is 2.5 meters above the ground. a) What is the speed of the skater at the bottom of the ramp? (ans. 7.0 m/s) b) What is the speed of the skater at height B which is 1.2 meters above the ground? c) How what is the height of the skater when her speed is 3.5 m/s? d) What is the maximum height that the skater will rise? m= 250 kg 35 m 3) According to legend Sisyphus is condemed by the gods to push a stone up a hill for eternity. Just before he completes his task the stone rolls to the bottom of the hill and Sisyphus must begin again. The hill makes an angle of 65 with the ground and Sisyphus moves the stone at a constant speed of 1.2 m/s a) Label the forces on the stone. b) What force must Sisyphus use to push the stone? 65 (ans. 2220 N) c) How much power must Sisyphus supply? (ans. 2670 W) d) How much energy does the stone gain and in what form! (ans. 77.800 M) e) What is the maximum speed of the stone at the bottom of the hill it it is allowed to slide withou friction? (ans. 25 m/s) f) How much time would it take a 1200 W motor lift the stone to its final height? (ans. 64.8 s)