A 55 kg skier is at the top of a slope, as shown in the illustration below. At t

Question

A 55 kg skier is at the top of a slope, as shown in the illustration below. At the initial point A, the skier is h = 9.9 m vertically above the final point B.

(a) Set the zero level for gravitational potential energy at B, and find the gravitational potential energy associated with the skier at A and B. Then find the difference in potential energy between these two points.

(b) Repeat this problem with the zero level at A.

(c) Repeat this problem with the zero level midway down the slope, at a height of 4.95 m.

Explanation / Answer

a) PE = mgh

assume up is positive

PEA (PE at A)= 55(9.81)(9.9) = 5341.55J

PEB( PE at B)= 55(9.81)(0) = 0J

difference in PE = PEA - PEB = 5341.55J

b)

PEA (PE at A)= 55(9.81)(0) = 0J

PEB( PE at B)= 55(9.81)(-9.9) = -5341.55J

difference in PE = PEA - PEB = 5341.55J

c)

PEA (PE at A)= 55(9.81)(4.95) = 2670.77J

PEB( PE at B)= 58(9.81)(-4.95) = -2670.77J

difference in PE = PEA - PEB = 5341.55J

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