Aloaded ore car has a mass of 985 kg and rolls on rails with negligible friction. it starts from rest and is pulled up a mine shaft by a cable connected to a winch. the shaft is inclined at 29.5° above the horizontal. the car accelerates uniformly to a speed of 2.20 m/s in 12.0 s and then continues at constant speed.
(a) what power must the winch motor provide when the car is moving at constant speed?
(b) what maximum power must the motor provide? (c) what total energy transfers out of the motor by work by the time the car moves off the end of the track, which is of length 1,250 m?

Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. so it is no surprise that such clothing has largely replaced thickand heavy old-fashioned coats. (a) consider a jacket made of five layers of 0.1-mm-thick synthetic fabric (k = 0.13 w/m·°c) with 1.5-mm-thick air space (k = 0.026 w/m·°c) between the layers. assuming the inner surface temperature of the jacket to be 28°c and the surface area to be 1.25 m2, determine the rate of heat loss through the jacket when the temperature of the outdoors is 0°c and the heat transfer coefficient at the outer surface is 25 w/m2·°c. (b) what would your response be if the jacket is made of a single layer of 0.5-mm-thick synthetic fabric? what should be the thickness of a wool fabric (k = 0.035 w/m·°c) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a five-layer ski jacket?