
3.9. For each of the following applications, sketch an appropriate probability density function for the
respective random variable. Explain your reasoning.
(a) A box is at rest on a horizontal table. A force is applied on the end of the box and the box
eventually moves as the force is increased, overcoming the static friction force. Sketch a reasonable
probability density function for the friction force.
(b) A ball is dropped from rest very high in the atmosphere. As it falls it is subjected to wind gusts
from all directions. The gust magnitudes comprise a random variable. Based on the acceleration of the
ball, sketch a reasonable probability den