Your lab results are to be turned in via Google Docs. Check your Google Apps account for a shared document called, "Paper Coaster Lab Data."
Background
An object will travel in a straight line until a force acts to change its path of motion. This means that to travel in a circle (or a loop) the force must act on an object to push it sideways.
When the force acts to push the ball to the inside of a circle, the force is called a centripetal force. It is the centripetal force that keeps you from flying out of your seat in a loop on a roller coaster. It is that same centripetal force that spins your clothes in a circle in the clothes dryer. With this centripetal force there is also an acceleration. This acceleration is called a centripetal acceleration. The centripetal acceleration also points to the inside of a curve or circle and is calculated from,
Where "ac" is the centripetal acceleration, "v" is the velocity, "R" is the radius. When you jump of a chair, it is gravity that pulls you down. If you were to get stuck upside down on roller coaster, gravity would also be pulling you down. But when the roller coaster is moving fast enough, the centripetal force pushes you towards the center with a greater force than or equal to the force of gravity. This is shown with the picture below.
This means that gravity does not have enough time to pull you out of your seat in the loop. If the roller coaster is traveling too slow, then gravity could win and pull you out of your seat.
(However, coasters are designed so this does not happen.)
Objectives
To find the minimum height necessary to make it around the loop without falling out.
To investigate the effect of the entering straight track's angle on making it around the loop.
Calculate the minimum g's needed to stay safely inside the loop
Materials
paper loop template
paper track template
scissors
roll of clear cellophane tape
ruler marked off in centimeters or meters
calculator
marble or steel bearing
Procedure
You are to make two straight pieces of track and tape them together.
You are to make a loop and tape it to the straight piece of track.
Prop the end of the straight track on a box or ring stand cross bar. Make sure the end is at least twice as high as the loop's height.
Hold a marble at the top of the track.
Use a ruler to measure the vertical start height to the bottom of the track under the marble.
Release the marble from rest.
Listen to the marble as it travels around the loop. You will hear it make contact with the loop during its entire journey.
Move the marble lower; release it from rest, and listen to see if it makes contact the entire way around the loop. Repeat this process until you gone too far down the track. You will know you have gone too far when you hear the silence of the marble as it looses contact with part of the loop. Then back up until you've reached the point where the marble just barely keeps in contact with the track as it complete the loop. VERY IMPORTANT:If the loop moves when the marble rolls around it, your results will be inaccurate. Hold the loop in place with your hands while doing the experiment. Keep this in mind when building your roller coaster.
Record this starting height on the data section of the lab.
Increase the angle of the straight piece of track. Do make the angle extremely steep.
Repeat the loop process until the marble just barely keeps in contact with the track as the marble makes it around the loop.
Record this starting height on the data section of the lab.
by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)
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