# Air resistance and acceleration

Discussion in 'MCAT Study Question Q&A' started by m25, Sep 5, 2014.

1. ### m25

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If we are taking air resistance into account, when two objects of different masses are dropped, is the lighter object experiencing less acceleration in the downward direction?

2. ### Cawolf 5+ Year Member

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If we look at two objects that are identical except for mass we can compare.

Lets say the more massive object has mass M, and the lighter object is mass m = 0.5M.

Just looking at vertical forces. We can also state that the drag forces will be identical, since it is not based on mass, so drag force = D.

Massive
F = MA = Fd + Fg = D - Mg

Ma = D - Mg

A = (D - Mg)/M = (D/M) - g

From that calculation we know the acceleration of the lighter object is a = (D/m) - g

a = (D/m) - g = (D/0.5M) - g = (2D/M) - g

So more massive object A = (D/M) - g < a = (2D/M) - g

Therefore we know the lighter object is feeling a more positive upwards force (or less force downwards).

Since the lighter object has less downwards force, it experiences less downwards acceleration.

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Last edited: Sep 5, 2014
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### m25

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Ah, perfect. Thank you!

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