Can someone help me please? thank you

Which is not a characteristic of a heat pump? a. it is used in air conditioners. b. it uses a refrigerant. c. it requires no work. d. it reverses the normal flow of thermal energy.

Astudent weighing 700 n climbs at constant speed to the top of an 8 m vertical rope in 10 s. the average power expended by the student to overcome gravity is most nearly

You fire a bullet into a 3 kg wooden block attached to a spring with spring constant 70 n/m. when the bullet strikes the block, the spring compresses. the bullet has a mass of 0.03 kg and strikes the block with a speed of 200 m/s. what is the speed of the block and bullet when they first start moving together?