Suppose that a random man's height from a certain population has a normal distribution with mean of 70" and standard deviation of 3 and a random woman's height has a normal distribution with mean of 66' and standard deviation of 4". find the probability that a random woman is taller than a random man. (hint: the sum of two gaussian random yariables is a gaussian random variable with μ-hs and a variance of σ2-σ2+ ơy2).

C. The net force is perpendicular to the motion.

When you swing a yo-yo in a circle around your head, the net force
is the tension in the string, pointing toward the center of the circle. 
There's nothing there that provides any force parallel or opposite to
the motion.

When the Earth revolves around the Sun in a circular orbit, the net force
is the gravitational force between the Sun and the Earth.  There's nothing 
there that provides any force parallel or opposite to the motion.