Which of these physical settings make sense for the object in question 1, whose position is given by a(t) = -3 cos(t)?

Question

A car driving from San Diego to Los Angeles.

B. An ant walking at a steady pace from the tip of a propeller toward the hub.

C. A skydiver falling from a plane, before she opens her parachute.

D. None of these.

E. The shadow cast by a rock that's stuck on the edge of a spinning wheel.

Answer 1

Since the equation models cyclic motion where the movement goes back and forth from -3 to +3 we can rule out choices A and C pretty easily.

For E, If you imagine a wheel of radius 3 laying its side, the rock's shadow would move left and right as the wheel goes around. The furthest left it would go is 3 to the left and back to the middle and then 3 to the right, repeating like a sine wave, so this is the answer.

Its not B (even considering a spinning propeller) because the ant's peak left and right amplitudes will be getting smaller as it gets closer to the center hub.

It's also. a little confusing because at first I thought this might be an acceleration, because they're using the variable "a", but it explicitly says its a "position" equation.