# mousetrap vehicle science

## Mousetrap Vehicles: Power Output

February 03, 2012

Power is the rate at which work is done or the rate at which energy is being used. Learn all about power output and how it applies to mousetrap powered vehicles.

Power output is the rate at which energy is being used. There is no difference in the amount of energy expended when you walk up a flight of stairs and when you run up a flight of stairs, but there is a difference in the amount of power output in the two situations. The power expended by running up the stairs is much greater than by walking up the same flight of stairs. Because running up the stairs allows you to get to the top more quickly you use energy at a much higher rate. Higher power ratings mean that more work is being done per second when compared to smaller power ratings. A watt is the unit of measurement for power. A 120 watt light bulb uses twice the energy each second compared to a 60 watt light bulb.

P = W/t

formula: power [p] is the work [w] per time [t]. Power is measured in watts, work is measured in joules, and time in seconds.

In a perfect universe where there was no friction, running up the stairs compared to walking up the stairs would have no difference in the total energy consumed but in our real world environment friction will make a difference. In our non-perfect universe, where heat and sound are real forms of friction, an object that consumes energy at a higher rate will also lose more energy to friction when compared to the same object with a lower power output. The force of friction is always greater with higher energy outputs causing slower moving objects with smaller power outputs to be more efficient. A vehicle traveling at 55 mph will be more efficient that the same vehicle traveling at 70 mph and therefor will travel much further on the same tank of gasoline (but Doc Fizzix likes traveling fast so this is a mute point). The advantage of high power outputs is that you can get more work done in a shorter amount of time. If your goal is to get to the finish line before everyone else then you want to have the highest possible power output knowing that you will consume more energy than everyone else.

bonus tip: Heat and sound are forms of energy caused by friction.

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