Help?
( this is not from a quiz. )
( also, this is science. )

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

What’s #16 asking me and how do i solve it?

Amachinist turns the power on to a grinding wheel, at rest, at time t = 0 s. the wheel accelerates uniformly for 10 s and reaches the operating angular velocity of 96 rad/s. the wheel is run at that angular velocity for 40 s and then power is shut off. the wheel slows down uniformly at 1.5 rad/s2 until the wheel stops. in this situation, the time interval of deceleration is closest to: