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- b) Draw the force vectors showing the direction of the force for the positions of the roller coaster noted.
7. The gravitational force Fg is acting on the car at all times. To move in a circle, there must be a force toward the center of the circle. At the top of the circle, the gravitational force is toward the center of the circle. For a car at the bottom of the circle, the gravitational force is in the opposite direction to what is required for circular motion. The only other force at the bottom of the loop is the track pushing up on the car. This upward force must be responsible for the car moving in a circle.
- a) Draw the gravitational force and the track's force on the car when the car is at the bottom of the loop and moving in a circle.
8. Check your force diagram for the car at the bottom.
- a) Is the gravitational force (or weight) vector pointing down?
- b) Is the force of the track pointing up?
- c) Is the force of the track pointing up larger than the weight vector pointing down?
9. The force of the track on the car is called the normal force FN. (It is called the normal force because it is "normal" or "perpendicular" to the track.) This normal force must be present on the car when it rounds the loop at the bottom.
- a) Could the normal force at the top of the loop be zero?
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