Question

1) (Boy sledding on hill) A boy on a sled (total mass of boy-plus-sled m = 34 kg) slides down a straight, snowy incline of length 4-236 m angled at a-15° with the horizontal. At the base of the hill is a tiny dip, after which the boy begins sliding up another straight hill, traveling a lern gth L2-40 m at an angle of θ2-300 with the horizontal. The boy starts from rest and ends at rest. Only gravity and friction act on the boy a) Compute the total work done by gravity (from start to finish) by directly using the definition of work. In other words, compute the work done by gravity as he sleds down the first hill and, separately, the work done by gravity as he sleds up the second hill, taking account of the angles and lengths of the hills. b) Compute the total work done by gravity (from start to finish) by instead using the concept of gravitational potential energy c) Use your answer to the previous part to calculate the total work done by friction (from start to finish). d) In words, physically interpret your frictional work answer to previous part as an energy transfer (i.e., energy was transferred from what and deposited into what?)

Answer 1