An asteroid that slammed into earth about 65 million years ago (low on the dinosaurs' hit parade) was estimated to be about 8 km in diameter and about 10^15 kg in mass. a) if a similar asteroid headed toward earth now with a speed of 21 km/s, how much kinetic energy would it have? b) compare this answer to the energy used by the us in one year (about 10^20 j) and discuss. problems - the principle of conservation of energy a (not -so -super) ball dropped from 50 cm rebounds to a height of 33 cm. find a) the fraction of the original energy lost and b) the speed with which the ball left the ground after rebounding. c) where did the lost energy go? zartan of the jungle (him again) crosses another river by grabbing a 9 m long vine and swinging over the water, it the vine starts out at angle ot 17 degree, to the vertical, use the principle of conservation of energy to find zartan's speed at the bottom of the swing. a skier starts from rest 7 m above the horizontal, and slides down a frictionless slope. the skier then encounters a rough horizontal surface (mu k = 0.3) as shown. how far does the skier travel along the rough surface before she stops?