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Do heavier objects fall faster than lighter ones?

If you have two balls which look the same, but have different masses, which will be the first to reach the ground?

People often believe that the heavier ball will fall more quickly. They think that gravity acts more on a heavier object thus pulling it down faster. In fact, gravity works independently of mass. This means that all objects should fall at the same rate. Galileo is said to have tested this idea by dropping balls of different mass from the Leaning Tower of Pisa.

In practice the speed that objects fall may vary, because air resistance will act on objects pushing them up slightly, in opposition to gravity. The greater the surface areas of an object the more surface for air to push up against and so air resistance will act upon a falling object, slowing its fall. The amount of air resistance acting upon something is dependent upon its shape and size. A large parachute slows the fall of a person, bringing them slowly to the ground. If there is no air resistance, or the same amount of air resistance, then objects of the same mass will fall at the same rate.

Famously, astronauts on the Apollo 15 Mission, demonstrated this phenomenon on the moon by dropping a hammer and a feather at the same time. As there is no air on the Moon, there is no air resistance to slow the fall of the objects. It could be seen that even though the objects had different masses, they fell at the same rate.


In the comments below, suggest a way that you would introduce this concept to your class.

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This article is from the free online course:

Teaching Primary Science: Physics

National STEM Learning Centre