Arock at the top of a 30 meter cliff has a mass of 25 kg. calculate the rock’s gravitational potential energy when dropped off the cliff. assuming that energy is conserved and there is no air friction and gravity is 9.8 m/sec., at the bottom of the cliff the rock’s potential energy is completely converted to kinetic energy. use the formula for kinetic energy to calculate the rock’s speed at the bottom of the cliff. show all calculations.

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in

Which of the following situations would produce an average velocity of zero? o a. a horse galloping in a field b. a round-trip to school and back o c. a trip, first to the moon, then onto mars o d. the criss-crossing path of a flying bug

4.at 0 ºc, some amount of energy is required to change 1 kg of water from a solid into a liquid. if you had a 2 kg piece of ice, what effect would this have on the amount of thermal energy required to change the water from a solid to a liquid? it would require more energy to change solid water into liquid water because there are more molecules in this larger piece of ice. it would still require the same amount of energy to change solid water into liquid water because the entire piece of ice would still gain the same amount of energy in each case. it would require energy to be removed from the 2 kg piece of ice. the larger piece of ice already has more total energy than the smaller piece of ice, so energy must be removed for the ice to become liquid. it would require less energy to change solid water into liquid water because the energy would spread through the ice more quickly and the ice already has a larger total amount of energy because it is larger than a 1 kg piece of ice.