The speed needed at the bottom of a loop-the-loop track so that a car can coast to the top, with sufficient speed to stay on the track, depends on the mass of the car. (Neglect the effects of friction.)
A) sometimes true, since kinetic energy is a function of mass
B) never true
C) sometimes true, since potential energy is a function of mass
D) always true, since kinetic energy is a function of mass
E) always true, since potential energy is a function of mass

Question

Quizplus · Accepted Answer

The speed needed at the bottom of a loop-the-loop track for a car to coast to the top and stay on the track does not depend on the mass of the car. This is because both kinetic energy (needed at the bottom) and potential energy (at the top) are proportional to mass, so when calculating the speed necessary, the mass cancels out. This principle is a result of the conservation of mechanical energy, assuming no energy is lost to friction or air resistance.

The Speed Needed at the Bottom of a Loop-The-Loop Track