Question

A rope is tried to a tree limb and used by a swimmer to swim into the water below. The person starts from rest with the rope held in the horizontal position at a height of 35.0 m, the swimmer swims downward, and then let go of the rope. If the frictional force is neglected,

a) what is the work done by the tensional force of the rope?

b) what is the speed of the person as he let go of the rope?

c) if the person is clocked at a speed of 20.0 m/s as he let go of the rope, what is the work done by the frictional force?

Answer 1

a) we know that work done is given as

W = force * distance * cos

here = 90 between tension force and direction of motion,

so,

cos 90 = 0

so,

work done by tension = 0

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b) at initial point, person had potential energy = mgh

this is converted to kinetic energy as he moves down

(NOTE - REMEMBER, I AM USING CONSERVATION OF ENERGY BECAUSE WE CAN NEGLECT FRICTIONAL FORCE AS PER THE QUESTION)

mgh = 1/2mv²

v = sqrt (2gh)

v = 26.2 m/s

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c) work done = change in kinetic energy

for this i need mass of the person.