# how is it that heavier objects don’t fall faster (e.g. Pisa experiment) , but heavier people go faster downhill on skis or sleds than less heavy people

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Edit: thanks all for your examples!

In: 3

There are different forces at work when interacting with the ground.

In the air, gravity pulls mass with a certain force, and inertia in the object resists that force so that everything accelerates at the same rate. However, when you introduce a slope and differing friction into the mix, you will get different speeds.

Let’s say a light person weighs 60kg and that lets them ski at a certain speed. Someone weighing 120kg has twice the force of gravity, but negligibly more friction in their interaction with the surface of the snow. They are “closer to freefall” in the respect that they are proportionately less affected by the sliding resistance.

Hope this helps. 🙂

Larger mass equals larger kinetic energy .. once an object is in motion it tends to stay in motion…

This is bigger guys can get more speed going down hill over you skinnier guys…

There are other factors at play like length of boards/skis and the additional friction that will offset any speed advantages…

Heavier objects fall faster through air and friction. While the acceleration of gravity is the same, the resistance to motion is effectively less.

A 180lbs force pulling a person down from gravity will get them moving faster and faster until 180lbs of drag and friction are resisting them. If you did this with a 120lbs person, you need less drag/friction to resist them and so a lower top speed.

Friction.

In the bowling ball vs feather comparison they fall at the same speed without atmosphere to slow the down. The air friction from the atmosphere is what makes a feather fall slower in normal life.

It’s the same thing on snow. Friction from sliding is overcome from higher mass but not low mass.

It’s also a bit more complex than this, the nature of the snow can result in the opposite effect. Consider a heavy skiier with small skiis would sink into the snow (increasing the friction) while a lighter skiier with large skiis would not compress the snow and glide over it.

Lets look at gravity, it exerts a force of 9.81 N per kg of mass. The formula for acceleration is the acceleration is force/weight. If you combine these 2 the weight drops out so acceleration is independent of weight.

However on earth there is air resistance so the larger your frontal surface is the more air resistance you have, this is why a kilogram of feathers would fall slower than a kilogram of lead on earth, but both would fall just as fast on the moon.

Heavier people have more weight relative to their frontal area and are able to go faster.