Science Buddies: "Ask an Expert"

Hi! Need some help for my son's science fair project about gravity and falling objects. He is supposed to make different objects fall at the same time from the same height to test if they hit the ground at the same time or not. We are having a hard time selecting the objects. We need 2 objects of same mass, 2 objects of same size, but different mass, and two objects of different size/shape but same mass. Could you post recommendations of household items we can use? Thanks in advance!

Hi - the first thing that comes to mind for me is balls from different sports. Ping pong ball, golf ball, tennis ball, pool ball, whiffle ball, baseball, softball, soccer ball, basketball, etc. There you have a big list of things that are all the same shape - I think you should be able to find two that are pretty close in diameter, but different mass (ping pong vs golf or whiffle vs softball?); and two that are the same mass but different size (this one is a little harder to guess, but if you weigh them all, you could check). Then for different shapes, just weigh random objects from around your house that won't break if you drop them (e.g. don't use a coffee mug) and find one that's close to one of the balls.

Alternatively - you could use a variety of cardboard boxes. The box itself determines the size and shape (e.g. a big square box vs small square box, square box vs long skinny box), and you can fill them with different objects to change their weight.

Hope that helps!