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One site said the total forces is the sum of the vectors. My homework question is "A skydiver of mass 90 kg is falling with a terminal speed of 60 ms-1. What does that mean? What is the total force acting on the skydiver?(g=10ms-2)

My reasoning is that since he is falling at 60ms^-1 and his mass is 90kg that therefore the total force is 5400N but I am not sure. Do you have to + 900N for weight and also minus what air friction does to the skydiver? or am I over thinking this?

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  • $\begingroup$ Hi.....wondering about your first sentence, is it out of place in your question? Or could you expand on it a bit more. Just confused by it. Thanks a lot $\endgroup$
    – user74893
    Mar 25, 2015 at 0:53
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    $\begingroup$ Note that force is mass times acceleration while the 60 m/s is a speed; thus your "5400 N" isn't actually a force. $\endgroup$
    – Kyle Kanos
    Mar 25, 2015 at 1:30

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Since he is falling at terminal, hence constant, velocity, he is experiencing NO net (total) force. There are (at least) 2 forces acting on him though, which are his weight (900N) and the air resistance. Because he has constant velocity, i.e. he is not accelerating, these forces must balance, i.e. the air resistance is 900N upwards whilst his weight is 900N downwards. The vector nature of force enters the picture in the up and down directions.

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