# Climber hanging from a cliff

1. Feb 25, 2010

### pediepit

1. The problem statement, all variables and given/known data

A 65 kg climber finds himself dangling over the edge of an ice cliff, as shown in the figure below. Fortunately, he's roped to a 940 kg rock located 51 m from the edge of the cliff. Assume that the coefficient of kinetic friction between rock and ice is 5.7×10−2. What is his acceleration, and how much time does he have before the rock goes over the edge? Neglect the rope's mass.

2. Relevant equations

Rock
FT - Ff = massrock * a
N = massrock * g

Climber
FT - massclimber * g = massclimber * a

3. The attempt at a solution

I solved for FT for the climber and then stuck this equation into FT in the rock equation. Then solved for a.

a = (g(massclimber - Mu(k) * massrock)) / (massrock - massclimber)

Plugging the numbers in the equation, i get a = 0.127904 m/s2 My homework tells me this is wrong and I can't figure out why. any help is appreciated!

2. Feb 25, 2010

### ƒ(x)

What's the force of friction?

What is the books answer btw?

3. Feb 25, 2010

### pediepit

Ff = Mu(k) * N or Mu(k) * massrock * g

it's actually homework on the computer and doesn't give me the answer. Just tells me mine is wrong and to try again!

4. Feb 25, 2010

### pediepit

figured it out

FT - massclimber * g = massclimber * a
should be
FT - massclimber * g = -massclimber * a
since the climber is moving downward