Materials Needed:
- Ramp (plank of wood)
- Simple car chassis (derby car)
- Different shapes to attach to chassis
- Pieces of Foam core
Procedure: (see Figure 8)
- Set up a ramp as shown.
- Identify a starting line.
- Release the simple car chassis until it repeatably rolls
to the same place.
- Mark the location.
- Repeat with different frontal area (sheets of foam core of
different sizes and orientation), keeping the weight of
the car consistant. Try a very large frontal area.
- Mark the locations they roll to.
- Which tests went the farthest? Smallest frontal area or
largest?
- Repeat these steps using different steamlined shapes as you
did with the nose cone on the soda can. Be careful to keep
the other variables constant.
- Why is it invalid to use different test cars (chassis)? What
other physical properties can affect the amount of distance
traveled?
Figure 8: Aerodynamic shape investigation setup
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Observations:
Roll-down tests are used by some automobile manufacturers, race car
builders, and car testing organizations (among others) to test the
aerodynamic drag of a car. The idea is to roll a car (with the engine
turned off and out of gear) down a hill, and see how far it rolls. A
car with more drag (for example, a car with a parachute behind it) will
roll to a stop faster (or in a shorter distance) than a streamlined, low
drag car.
In this case the frontal area did change. Make observations on how
the frontal area and shape can affect the drag or resistance the
air has on your vehicle.
How can you apply these principles to your car to make it faster?
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