# Tarzan problem

1. Jan 9, 2007

### mikesown

"Tarzan" problem

1. The problem statement, all variables and given/known data
"Tarzan (m=85kg) tries to cross a river by swinging from a 10.0m long vine. His speed at the bottom of the swing, just as he clears the water, is 8.0 m/s. Tarzan doesn't know that the vine has a breaking strength of 1.0 x 10^3 N Does he make it safely across the river? Justify your answer."

2. Relevant equations
$$F_{c}=\frac{mv_{t}^2}{r}$$

3. The attempt at a solution
I attempted to substitute in the variables as such:
$$F_{c}=\frac{85kg*\left(8.0\frac{m}{s}\right)^2}{10.0m}$$
I got 544N, which is not the answer(1.37x10^3N is his 'weight' at this point, greater than the rope). Am I missing something obvious?

2. Jan 9, 2007

### Gib Z

You do not have the right formula. You are thinking of Centripetal Force, this is Pendulum Motion.

3. Jan 9, 2007

### PhanthomJay

You have correctly identified the centripetal force as 544N. The centripetal force is the net force acting up toward the center of the circle. The net force is a combination of the tension force up and his weight (not his 'weight' as you have described...his weight is m*g) down. Solve for T. Does the rope break?

4. Jan 9, 2007

### ShawnD

This is correct. Add 544N to (85 x 9.8) and you get 1377N

5. Jan 9, 2007

### Gib Z

Is it too late to pretend I havent said anything? eep my bad, just ignore anything i say