Slow Coaster
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Prompt:
create a track using the provided materials. Roll the ball and time how long it takes to roll down the whole track.
Questions:
Can you make the ball roll slower than Jeffs Mom walks?
Materials:
Rubber Bands
1/4” x 3” carriage bolts
1/4" Hex Nuts
1/4" Wing Nuts
2’ x 2’ pegboard
Basic Assembly
The bolts screw onto the pegboard, held in place by a nut on the front, and a wingnut on the back. Rubber bands are stretched from one bolt to the next, and sit parallel to the pegboard.
Exploration with Design
Initial thoughts and process:
As a group, we brainstormed some different kinds of track that might be slow moving. Small declines, flat track, maybe even an incline? We figured that a very slight decline would be a good place to start, and may be our most effective method of achieving a slow roll. We had trouble creating enough momentum for the ball to roll up an an incline. We found that the longer the ball rolled, the more momentum it would pick up. We also noticed that the tautness of the rubber bands, and how far they were from the peg board effected the speed of the ball.
Notes and Observations:
In some spots, the ball was rolling off the sides. To fix this, we created "walls" for it to bounce off of and continue rolling down the track. On this trial we were able to get the ball to drop and roll flat, but not for a signifigant distance.
The Science of Motion
Key Terms to Understand:
Unbalanced Force- when the force applied in one direction is greater than the force applied in the opposite direction.
Gravity- the force holding everything down to the earth. A force that tends to speed things up when they are falling
Inertia- an object in motion likes to stay in motion. An object at rest likes to stay at rest (Objects are stubborn!)
When you drop the ball, gravity pulls it down, and the balls inertia keeps it moving along the track. Unbalanced forces created by bands on the track may cause the ball to change direction, speed up, or slow down. The rubber bands create friction on the ball, so you can manipulate the forces on the ball by changing the size and placement of the bands. You can also create walls and ramps to manipulate the forces being put on the ball, and control its speed and direction.
How does the coaster work?
Videos for a better understanding of motion:
Jeff Goodman goes more in depth about Motion, and Newtons laws
Final Design
The final design of this coaster includes four long, shallow declines, one short decline, and one long flat stretch before dropping into a basket.
Speed Calculations
To calculate speed, divide the length of the track by the time it takes the ball to complete the coaster.
Distance/ Time = Speed
Track Length: 302cm
Time: 16.28 seconds
Speed: 18.55 cm/sec
Conclusions
Our coaster achieved the goal, and moved slower than Jeffs mom. She moved 5 M (500 cm) in 20 seconds, which means her speed was 25 cm/second. "Fallingwater" slow coaster has a speed of 18.6 cm/ second. Because fallingwater moves less distance in the same amount of time, it is slower than Jeffs mom.
Related Content: check out these cool videos!
These brothers have used the science of motion to create massive marble runs and races. Rather than aiming for slow rolls, they create tracks and manipulate forces with the goal of increasing speed. Their videos show countless examples of gravity, friction, inertia, and opposing forces in action. Check out their youtube channel for more fun motion videos!