# Real quick mechanics questionWatch

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#1
A particle of mass m falls from rest against an air resistance mkv, where k is some constant and v is its speed.

Show that the speed of the particle tends to a limit g/k.

So ma = mg - mkv

a = g - kv

Can I just say a = 0 and then v = g/k?

Or do I have to do the whole dv/dt = g - kv... write v in terms of t and let t tend towards infinity thing?
0
11 years ago
#2
I would personally do the latter, unless you can show nicely that as t->inf, then a->0
0
11 years ago
#3
I'd resolve forces and use F = ma to find the acceleration, integrate it to find velocity and use the conditions when v or something
0
11 years ago
#4
I'd say - as a 'tends to' 0, kv - g 'tends to' 0

Thus, k 'tends to' g/v
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