A ski is placed on snow will stick to the snow. However, when the ski is moved a

Question

A ski is placed on snow will stick to the snow. However, when the ski is moved along the snow, the rubbing warms and partially melts the snow, reducing the coefficient of kinetic friction and promoting sliding. Waxing the skis makes it water repellent and that on a gentle 200m slope in the Alps, a skier reduced his top-to-bottom time from 62.0s with standard skis to 44.0 s with the new skis. Determine the magnitude of his average acceleration with a) standard skis b) the new skis assuming a 3.20 degree slope, compute the coefficient of kinetic friction c) standard skis d) new skis

Explanation / Answer

The accelerations are easy enough to find. Here's how:

Given time (two values--one for each ski type), initial velocity (assume zero...I know the semantic problem here) and distance (200m), one finds acceleration by using the kinetic equation:

distance = 1/2 * acceleration * time^2 + initial velocity * time

To get the coef. of kinetic friction, use Newton's 2nd law:

mass*acceleration = mass* g* sin(4.0) - MU*mass*g*cos(4.0)

where we know everything but MU.

From here it is just an 8th grade exercise in using a calculator.

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