How Did We Do That?!

We got your computer to time the swinging mouse. And then we used a really cool equation physicists have worked out that takes into account the Earth's gravity (which is what makes a pendulum swing) and the number pi. (Pi is a little more than 3. It shows up whenever something moves back and forth.)

Here's the equation:

And it means:

the length [L] of a pendulum (distance from your hand to the middle of the mouse)
equals
the strength of gravity on earth [g] (980 centimetres/second2)
multiplied by
the square of (the number of seconds [T] for one swing divided by two times pi)

When you plug the numbers for pi and gravity into the equation, the distance in centimetres works out to 25 times the square of the time per swing. (In inches, it's 10 times the time per swing squared.)

Try another look at that equation.

If you increase the distance from your hand to the mouse, then the time per swing ought to increase as well.

Try it!

What do you think would happen if gravity on Earth were stronger? Would a pendulum swing faster or slower? (Take a look at the equation again, you can figure it out.)

Watch out!

The equation doesn't work very well if you swing your mouse too hard. And it's tricky to figure out what measuring to "the middle of the mouse" means.