2. A 70 kg skier is at the top of a hill with height 60 m A) (2 pts) How much wo
ID: 1796124 • Letter: 2
Question
2. A 70 kg skier is at the top of a hill with height 60 m A) (2 pts) How much work does gravity do as the skier goes down the hill? B) (3 pts) The skier assumes the hill is completely frictionless. If he skier starts from rest, what velocity should he expect to have at the bottom of the hill? C) (2 pts) The skier measures his velocity at the bottom of the hill to be 30 m/s. This is less than the velocity he calculated assuming no friction. He, having just taken physics, knows that the discrepancy is due to friction. Calculate much energy was lost to work done by friction.Explanation / Answer
A)
work done by gravity = m*g*h = 70*9.8*60 = 41160 J
B)
from work energy relation
work = change in Ke
W = (1/2)*m*(vf^2 - vi^2)
41160 = (1/2)*70*(vf^2-0^2)
vf = 34.3 m/s
============
C)
energy lost to work done by friction = Wg - dKE
Wf = 41160-(1/2)*70*(30^2-0) = 9660 J
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.