# Circular motion & tension

1. Oct 13, 2009

### joemama69

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

A rock is whirled at the end of a rope in a vertical circle

Find a general expression fo the Tension

What is the magnitude of the total acceleration

2. Relevant equations

3. The attempt at a solution

$$\sum$$Fr = ma = T + mgcos$$\theta$$

T = ma - mgcos$$\theta$$ not sure

a = (T + mgcos$$\theta$$)/m not sure
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 13, 2009

### rock.freak667

At an angle θ to the vertical, what is the component of the weight along the line of tension?

3. Oct 13, 2009

### joemama69

not sure what u mean

4. Oct 13, 2009

### rock.freak667

Draw the mass at angle θ to the vertical.

Can you split the weight mg into two components?

5. Oct 14, 2009

### joemama69

into two components, would that be the tangental compenent in the direction of the velocity and the second pointing towards teh center

6. Oct 14, 2009

### rock.freak667

actually it points opposite to the velocity and away from the center. What are these two components in terms of the angle?

7. Oct 14, 2009

### joemama69

Component along line of tension ma = mgcosQ

how do i do tat for the velocity, do i integrate that

8. Oct 14, 2009

### rock.freak667

the component is mgcosθ.

So the T points towards the center and the mgcosθ points away from the center. What is the resultant force equal to ?

9. Oct 15, 2009

### joemama69

Fr = T - mgcosQ = 0