Science Buddies: "Ask an Expert"

I am trying to determine the control, constant, independent and dependent variables in the following from an episode of Myth Busters.

Problem: Can a motorcycle traveling at highway speed drive across the surface of a lake?

This a summary of the episode.
Adam and Jamie set up a small-scale test using a remote-controlled toy motorcycle and a fabricated small pond of scaled depth, but in all their test runs, the high-speed camera showed the RC motorcycle riding mostly along the bottom of the pond. They next attempted to see if a motorcycle could actually achieve buoyancy on water; to do this, they built a rig to attach a motorcycle wheel to the side of a speedboat, and despite some initial difficulties getting the boat up to speed (solved by having Jamie counterbalance the added weight on the rear of the boat by lying on the bow), were eventually able to get the tire to skim on the surface at 60 miles per hour (97 km/h). They then enlisted AMA supercross veteran Eric McCrummen for a full scale test; McCrummen successfully rode his motorcycle across stretches of open water 50 and 100 feet (30 m) long with a depth of 3 feet (0.91 m), confirming the myth. Finally, Jamie attempted to determine if the motorcycle was merely skipping across the surface of the water on existing momentum or was in fact able to generate power on top of the water; this proved to be the former, as on his second attempt to ride across a much deeper and longer portion of the lake (after his first attempt went awry due to safety measures altering the motorcycle), he made it about 300 feet (91 m) before the motorcycle sank into the water.

Hi tlouis1324!

In order to determine what each variable is from the episode, you need to know the basic characteristics and definitions of the variables. A controlled variable is one that is constant and is unchanged in an experiment. It is held constant in order to observe the result of the independent variable. An independent variable is the variable that is being changed in the experiment in each trial, while a dependent variable is the one that is being measured. The dependent variable is affected and influenced by the independent variable, thus is the result of the experimentation.
For a more detailed explanation you can visit the following science buddies page on different types of variables:
https://www.sciencebuddies.org/science- ... bles.shtml

Hopefully this helped and you can use this to determine the variables. Let us know if you have any questions.

Good Luck,
nikhita8

Thanks for your speedy reply Nikhata.
I read the terms on this site and others, but I am still having trouble figuring out how to correctly identify some of terms. This is what I came up with, but I am still not sure. Do all experiments have a control?

Independent variable: Speed (this changed from 60mph to 80mph)
Dependent variable: ability of the motorcycle to travel across the lake (affected by the speed of the bike)
Constant variable: Surface of the lake (smooth and calm) (this remained the same in all attempts)
Control: weight of bike and rider (the type of bike and riders changed)

Please help me out.

Hi tlouis1324,

First, the controlled variable is the same as the constant variable. In this case the controlled variable would be the lake's depth and the weight of the rider. However there is also something called the control group which is a trial in which the original/natural independent state. There is more info on it on the following page:
https://www.sciencebuddies.org/science- ... l#overview
In this experiment the control group would be the motorcycle without the rig.

The independent variable is actually not the speed, but it was the attachment of the rig on the motorcycle. Speed is not the independent variable because they were testing to see the boat could achieve buoyancy on water. The change to the motorcycle is the addition of the rig. The independent variables tested would have been 1.) motorcycle without a rig and 2.) motorcycle with a rig.

The dependent variable is the ability of the motor cycle to travel across the lake, which is determined by the speed and distance the motorcycle can go at. It is affected by the rig attached on to the motorcycle.

Hope this helped! Let us know if you have any more questions.

nikhita8

Thanks again! Now I get it! lol

Nikhata,
When watching the show, they mentioned they needed to following at all times:
1) smooth and calm lake
2) gentle land to water transition
3) water to land transition not too muddy

The weight of the rider did not remain constant because there were two different riders testing the theory. Would it still be considered a constant variable?
I just need clarification with that part.

Thanks you are making it much clearer!

Hi tlouis1324,

Because they had two different riders, it would not be considered a controlled variable if the weight difference was large. However, if the weights of the two riders are relatively close, it would not have made a big difference and therefore, would have been constant.

Good Luck!
nikhita8

Thanks again!