When you’re upside down at the top of a vertical looping roller coaster, why is the centripetal force acting on you the least of anywhere in the loop?
In: Physics
The centripetal force is actually constant, assuming the car is going at a constant speed, because the centripetal force equation is mv²/r – mass isn’t changing, assuming a circular loop the radius isn’t changing either, so if the car’s speed doesn’t change, the centripetal force is constant.
The reason you feel less force at the top is because the **net** force is changing, not the centripetal force. The main forces at work on the car are gravity and centripetal force. Gravity always pulls down, centripetal force always pulls towards the center of the loop. Centripetal force has to be greater than gravity in order for the loop to work.
So at any point in the loop, the net force is the difference between centripetal force and gravity. At the bottom, their signs are opposite, so instead of subtracting, you add them up. At the top, their signs are pointing the same way, so you subtract gravity from centripetal force. That’s why the net force is at its maximum at the bottom, and its minimum at the top.
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