A bullet that has a mass of 120g is fired horizontally at a block of jelly of mass 10kg that is suspended from the ceiling by a uniform rod of mass 5 kg. Unfortunately, the designer of the experiment didn't pick a large enough block of jelly, and the bullet passed through the jelly and kept moving. After the bullet passed through the jelly, the experimenters measured the bullet to have a speed of 20m/s and the jelly block swung to a maximum height of 68cm higher than its initial height. How much energy was lost to heating up the jelly and the bullet?

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?