# Homework Help: [basic] Mechanics of a model rollercoaster

1. Jul 21, 2011

### mroutlaw

Hi,

I'm new to this forum. Just a quick intro, my name Is Allen and I attend Collage and I currently study Year 10 Physics. We are just learning the basics of movement and such.

I have created a model roller coaster, the cart is a ball bearing weighing 0.0010 kg, it has to roll around a track made of plastic tubing. The whole track is 6.2 meters, it takes 3 seconds average to complete the track. The average speed is 0.483m/ps. The track has to have one hill (0.032m) and a must contain a loop the loop (size irrelevant). The track must stop the bearing at the end.

At the end of the prac, there are a number of questions the home-work wants you to think about. Some are pretty straight-forward easy, but some require allot more thinking. Some I either don't know completely or not completely know, here are some;

1. I know that the ball-bearing is accelerating at the first hill, this because negetive gravitational force is pulling the ball down because it overpowers the positive force (upwoulds). The gravitational force causes rapid acceleration, speeding up to it's average velocity. Would it be de-cellerating when it travels in a straight line? (The track goes down the first hill to start and travels in a straight line, then completes the loop the loop going into a straight line again then it stops at the end. The track has no turns and no bends) because it has no positive gravitational force to only negetive pushing it down, air resistance and no drag? Or does it de-celerate when it goes up the loop the loop because it has to climb?

2. To find out the maximum speed would I have to times the average speed (0.483m/ps) by two?
If so, would this be the speed at the bottom of the first hill? How?

3. How do you find out the amount of kinetic energy the ball-bearing had at the start and the end of the track?

4. Where on the ride would you experience the most g-force? Wouldn't it be when you suddenly accelerate? And also, when do you feel the least g's?

5. Could the ball return to it's original height when released? Why Not? Where has the energy gone? How do I calculate the amount of energy lost in Joules and Joules per meter of track?

6. If I changed my rollercoaster track to have only a single hill and a long flat that goes on forever, how far would the ball-bearing have to travel to come to a complete stop? Do I have to get the amount of kinetic energy and times it by the hills length?

Sorry about the many and long winded question, but my teacher gives us pages and pages of home work and allot of them I'm struggling with. I can't ask the teacher how to do them because he will be away on a two week excursion with his junior class and after that period my exam will be on. My substitute teacher doesn't know anything about physics, he's just there to make sure we're revising.

Help would be greatly appreciated!
Allen Peters

Last edited: Jul 21, 2011
2. Jul 21, 2011

### cupid.callin

Hi Allen! Welcome to PF!

The ball bearing will be in rolling motion (without slipping) when moving. there is a friction force acting on it even though its just rolling (though very small) and also air drag.
on loop the loop it will loose KE into PE and then gain back ... only loss will be due to friction again.
so only frictional force (and some heating too) will cause deceleration.

max speed will be at bottom of hill
you can use energy conservation to find this

for start use energy conservation like in previous part and for last part ... ummm well ... lets see what ideas you have in mind.

Sorry i dunno what G-force is. :tongue2: I'm just a high schooler ... DUH!!!