Work done by gravity question A skier of mass m glides down a hill of height h .

Question

Work done by gravity question

A skier of mass m glides down a hill of height h. He is subject to friction. His initial velocity is 0 and the final speed is v. Which of the following statements about the work done by the force of gravity is correct?

a. The work done by gravity is exactly 0.5mv^2

b. The work done by gravity is larger than 0.5mv^2

c. We do not have enough information to determine that the work done by gravity is either equal to, larger or smaller than 0.5mv^2. We would need to know the exact shape of the slope to evaluate the work integral for the gravitational force.

d. The work done by gravity is smaller than 0.5mv^2

Explanation / Answer

in this case, the change in kinetic energy is equal to sum of work done by friction and work done by the gravity.

W(gravity-W(friction)=change in KE

that is,

W(gravity=0.5mv2 + W(friction)

W(gravity>0.5mv2

therefore, the correct option is (b)

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