In the roller coaster loop-the-loop, the passenger will also experience changes in apparent weight. The normal force is an indication of the apparent weight, as it was in the elevator. A passenger on the roller coaster feels lighter at the top of the roller coaster. This is similar to the elevator because in both cases you feel lighter because acceleration is down. A passenger on the roller coaster feels heavier at the bottom of the roller coaster. Once again, this is similar to the elevator because in both cases you feel heavier because acceleration is up.
 In the slow-moving roller coaster in the chart, the apparent weight (normal force) at the top may only be 1100 N, while the apparent weight (normal force) at the bottom may be 7100 N. There are three locations that you can use to summarize the discussion on forces and weight. On a level track with the cart moving at constant speed, the sum of the forces must be zero. At the bottom of the hill or loop, there must be a net force toward the center of the circle to keep you moving in a circular path. |
  Roller coasters do not use loops that are circular. They use a clothoid loop (it has a big radius at the bottom and a small radius at the top). In this way, at the top of the loop the roller coaster is moving in a small circle, while at the bottom it is moving in a larger circle. This is done to ensure that the roller coaster car can make the turn at the top but not gain so much speed at the bottom that the person at the bottom would be pulling more than 4 g's. |
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