# Tarzan problem

"Tarzan" problem

## Homework Statement

"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."

## Homework Equations

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

## 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?

Related Introductory Physics Homework Help News on Phys.org
Gib Z
Homework Helper
You do not have the right formula. You are thinking of Centripetal Force, this is Pendulum Motion.

PhanthomJay
Homework Helper
Gold Member

## Homework Statement

"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."

## Homework Equations

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

## 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?
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?

ShawnD