# Physics

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A person of mass 83.8 kg escapes from a burn- ing building by jumping from a window situ- ated 25 m above a catching net.
The acceleration of gravity is 9.8 m/s2 .
If air resistance exerts a force of 109.1 N on him as he falls, determine his speed just before he hits the net.

• Physics -

mg = 83.8*9.81 = 822.1 N
so
Fdown = 822.1-109.1 = 713

a = F/m = 713/83.8 = 8.51 m/s^2

v = a t
h = (1/2) a t^2

25 = (1/2)(8.51) (v/8.51)^2

50 (8.51) = v^2

v = 20.6 m/s

• Physics -

46 mph

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