# Tension Problem when swinging on a vine

1. May 13, 2010

### lvlech

This is my first time taking physics in my life. I want to get the concepts down on this hw problem.

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

Tarzan swings through the jungle on a vine. At the lowest point of his swing, is the tension in the vine greater than, less than, or equal to the gravitional force on Tarzan. Explain.

2. Relevant equations

3. The attempt at a solution

Based on logic, isn't the tension on the vine at the lowest point equal to the gravitational force of tarzan because I was thinking if the tension was greater than the gravitational force on tarzan, then the vine would break? Is that correct?

2. May 13, 2010

### Staff: Mentor

Welcome to the PF!

Think about it this way -- is there a difference in the tension between if Tarzan is just hanging there, as opposed to swinging through an arc? What is different about his motion between those two cases?

3. May 13, 2010

### lvlech

If Tarzan was hanging there, there would definitely be tension because of Tarzan's weight pulling the vine down. When he is swinging, I think the gravitational pull would be the same, but the tension at different points on the swing would not be the same?

4. May 13, 2010

### Staff: Mentor

All correct statements. What do you know about centripital acceleration?

5. May 13, 2010

### lvlech

Hm... I know that acceleration would be going toward the center. Centripetal Acceleration should also be going towards the center?

6. May 13, 2010

### tiny-tim

Welcome to PF!

Hi lvlech ! Welcome to PF!
(what's the difference? )

Use F = ma …

how many forces are there on Tarzan?

if his speed is v, what is his acceleration?

7. May 13, 2010

### lvlech

The problem does not give any numbers. It is just asking what the lowest point of the swing on the tension be greater than, less than or equal to the weight of Tarzan. I think it is equal to Tarzan's weight because the rope tension could only support the max amount of weight of gravitational pull? If it is greater, the vine would snap? If it is less than Tarzan's weight, there should not be any tension.

8. May 13, 2010

### tiny-tim

Yes, but physics is equations

it usually helps to give everything names (m for mass, v for velocity, r for radius), and put them in an equation …

you didn't really think you were going to be able to get away with not using any equations, did you?

Anyway, answer those questions …

how many forces are there on Tarzan?

if his speed is v, what is his (vertical) acceleration?