A62.0 kg skier is moving at 6.80 m/s on a frictionless, horizontal, snow-covered plateau when she encounters a rough patch 4.80 m long. the coefficient of kinetic friction between this patch and her skis is 0.300. after crossing the rough patch and returning to the friction-free snow, she skis down an icy, frictionless hill 2.50 m high.
(a) how fast is the skier moving when she gets to the bottom of the hill?
(b) how much internal energy was generated in crossing the rough patch?

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

Astudent is performing an experiment comparing sound and light waves. the student gathers the following data. what conclusion does the student most likely make based on this data? light waves always travel the same speed; however, the speed of sound is determined by the medium that it travels through. all sound waves always have the same energy, so the temperature of the medium does not affect wave speed. light needs to vibrate particles, so it travels fastest in tightly packed solids, while sound does not need a medium, so it travels fastest in a gas. tightly packed particles in solids slow down the light waves; however, sound waves make particles bounce into each other, so they travel faster in solids.

6–43 a food department is kept at 2128c by a refrigerator in an environment at 308c. the total heat gain to the food department is estimated to be 3300 kj/h and the heat rejection in the condenser is 4800 kj/h. determine the power input to the compressor, in kw and the cop of the refrigerator.