Classroom Activity for 11-14
What the Activity is for
Do heavier objects fall faster?
The purpose of this activity is to challenge the common mistaken idea that heavier objects fall faster than lighter objects.
What to Prepare
- Two objects, one at least double the mass of the other – we'd suggest a melon and a peach
- A chair, ladder or balcony to give you a free-fall distance of at least 2 metre (more is better, but messier)
What Happens During this Activity
Encourage pupils to predict which of two objects will hit the ground first when released together from the same height. Allowing pupils to feel the difference in the force of gravity acting on the two objects before release is important. Encouraging a dialogue about which of the two is being pulled with a greater force is also important.
It is likely that a range of predictions will emerge from the class. Invite pupils to share their reasoning for these predictions before they see the event.
Take care when dropping heavy objects. Bouncing masses can be dangerous, as indeed can be falling ones. Two blocks of wood, about 200 g and 800 g, will do the trick and will not be adversely affected by wind resistance over a fall of a few metres.
Melon and Peach demonstration is also suggested as a teaching activity in the Gravity and Space episode in the SPT: Earth in space topic. Dropping a melon and a peach simultaneously from a great height (a second floor window is likely to prove suitable) will provide memorable proof that the mass of an object makes no difference to the rate of fall.
You should be aware of the mess which will be created by this demonstration. This can be minimised by placing a large plastic sheet on the ground. You also need to be aware of the fact that from too small a height the fruits will remain intact (no sensational explosion), while if they are dropped from too great a height air resistance might become significant and the two will not reach the ground simultaneously. The moral here is that practice makes perfect. This is certainly one of those demonstrations that makes physics fun and simply unforgettable!