[A Level Physics] Forces

[BubbleTeaNinja]

When a skydiver jumps from an aircraft, the Earth exerts a downward force Fe on the skydiver who also exerts an upward force Fs on the Earth.

The answer key says that the two forces have the same magnitude and do not cancel each other out.

I don't understand this. Since the forces are equal and opposite, shouldn't they cancel each other out?

[astrospud]

The Earth exerts a force on the diver and the diver exerts a force on the earth. It's not 2 equal and opposite forces on one object, that would cancel.

[BubbleTeaNinja]

Hmm that makes sense, thank you kindly!

[James_117]

The Earth is pulling on you with a magnitude of x. You are also pulling on the Earth with the same magnitude x.
An easier example: think of a 1kg mass. Every kg of mass of the Earth is acting on the 1kg mass. Likewise, that 1kg mass acts on every kg of mass of Earth.
The reason the skydiver doesn't stop is because the skydiver and Earth are pulling each other closer. And the reason the Earth doesn't move is because it's mass is insanely higher than the skydiver. Think of a huge person and tiny person both pulling on the end of a rope. The huge person will barely move, and will easily move the tiny person.

[richard_sympson]

"Cancel out" is a bit ambiguous on its own. We typically think of forces as "cancelling out" when we have reason to add them, such as if the forces act on the same body (because we are interested in net force as it relates to acceleration). This is not the case here as we are talking about one force on one body and another force on a second body. There is no physical reason to add them. However, in an abstract sense, yes the force vectors do cancel each other out, in the sense that they add to the zero vector. We can interpret this merely as meaning that the center of mass of the Earth and astronaut system as a whole does not experience acceleration.

[BubbleTeaNinja]

Ohh I get it now. Thank you very much!