Question

A 45 kg swimmer starting from rest can develop a maximum speed of 12 m/s over a distance of 20 m How much net force must be applied to do this ?

MUST SHOW WORK!

Answer 1

55m got it right on edg

Answer 2

F = ma = mΔv/t = m(vf - vi)/t = mvf/t (since vi = 0)

⇒ a = vf/t


While accelerating from rest to vf, the distance d the swimmer traveled satisfies

d = (1/2)at2

Then

d = (1/2)(vf/t)t2 = vf t/2 ⇒

t = 2d/vf

F = ma = mvf/t = mvf / (2d/vf) = mvf2 / (2d)

F = [45 * 122 / (2 * 20)] N = 162 N

If you also want to know how long the swimmer took to accelerate to vf,

t = 2d/vf = (2 * 20 / 12) s = 3.33 s