February 22, 2017

Homework Help: physics

Posted by puff puff on Sunday, September 17, 2006 at 5:46pm.

A skier of mass 70kg is pulled up a slope by a motor-driven cable. The acceleration of gravity is 9.8m/s^2. How much work is required to pull him 60m up a 30.7ยบ slope (frictionless) at a constant speed of 3 m/s? answer in units of kJ.

In this question, I think I gotta use mgh and 1/2mv^2 to calculate the energy but i don't know how. can anyone help me? thanks in advance!

Forget about kinetic energy in this problem. Since the pulling is being done at constant speed, the kinetic energy does not change and the speed does not matter when computing the work required.

The work energy required equals the change in potential energy,
W = M g H sin 30.7.
(H sin 30.7 is the change in altitude)
M = 70 kg
H = 60 m.

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