Be a young Galileo

Activity: Galileo and his Pendulums

One of the things that Galileo was most famous for was pointing out that something’s mass does not affect how quickly it falls to the ground. Tricky to see when there is air resistance and a lack of high places that are safe to drop heavy weights from!

You will need:

String
Modelling clay or plasticene
Weighing scales

What to do:

Take the modelling clay and make two pendulum bobs of different weights. Make one considerably heavier than the other, but not so great that the sizes are vastly different. Keep them spherical
Attach them each of them to piece of string of same length to make two pendulums.
Stick them in an open doorway or along a support, again make sure the string length is the same.
Pull them out to the same height at the same time and let go…
They should be swinging perfectly in unison, if you have made them carefully enough!

What’s going on?

Pendulums don’t just swing, the weights at the end are actually falling. The pendulum motion allows them to ‘fall’ for longer than they would if we chucked them out a window! Which means we can examine how different masses are affected by gravity.

When compared to a falling hammer or feather we might expect the lighter weight to fall more slowly than the heavier one. But if you watch your pendulums you’ll see this is not the case. It doesn’t matter what the mass is, all objects fall at the same rate, as long as you rule out air resistance. It is tricky to get rid of air resistance but you can minimise the effect by making the bobs similar sizes and spherical!