# Roller coster loop

1. Jun 5, 2005

### UrbanXrisis

When a roller coster does a loop, what part would the person feel the most force?

I rode a rollercoster several times and the time that I felt the most force was heading up towards the top of the loop. But the force felt throughout the loop should be constant right?

2. Jun 5, 2005

### Staff: Mentor

Start by identifying the forces involved. As you travel around the loop, what forces act on you? And which of these forces is the one that we "feel"?

3. Jun 5, 2005

### UrbanXrisis

I feel the centripetal force. It acts on me constantly as I go around the loop.

4. Jun 5, 2005

### Staff: Mentor

Centripetal means "toward the center". Centripetal force means "the force acting towards the center"; it is not a kind of force, like the force of gravity or the tension in the string.

Saying that the centripetal force pulls you towards the center is just like saying that a vertical force holds you up. Tell me the real forces that act on you as you go around the loop. A "real" force has an actor. For example, one force acting on you is your weight: the earth pulling you downward. But you can't feel your weight. What other forces act on you?

5. Jun 5, 2005

### UrbanXrisis

When I go around the loop, the seat is pushing against me. That's the real force. I feel as if I was being pushed into the seal. I feel this force strongest when I'm heading towards the top of the loop. This force is called the normal force?

6. Jun 5, 2005

### Staff: Mentor

Exactly right! (almost) Yes, it is this "normal" force that you feel; that's the real force of the seat pushing against you. That force and your weight combine to give you a net force which includes any needed centripetal component.

The part that's not right is your statement that you feel this force strongest at the top of the loop. Actually, that's the place where you feel it least. The normal force is greatest at the bottom of a loop (where the speed is greatest and gravity works against you). Of course at the top of the loop things are pretty strange, since the normal force acts the opposite to everyday experience -- the seat is pushing you down rather than holding you up.

7. Jun 6, 2005

### Chris Danger

Hi,

I think the reason why you feel the force greatest when heading towards the top of the loop is because thats when your speed is greatest. As you change direction you are accelerating (regardless of whether or not your speed is changing), and in this case, the force needed to accelerate you is the "normal" force provided by the chair. The acceleration is greatest when your speed is greatest, so naturally you feel less force as you head up towards the top (as your kinetic energy is being exchanged for gravitational potential energy).