# Homework Help: Motion Diagram

1. Sep 27, 2009

### synergix

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

Mass of ball=0.500kg string length=1.02m
I have a motion diagram of a ball being spun in a counter clockwise direction. there are four points on the circular diagram this is the best I can do right now

...................v= 4.0m/s
....................|
....................|
v=6.0m/s ---------- v= 6.0m/s
....................|
....................|
................v=7.5m/s

calculate the value(in N) of the net force at the top point. What law are you using?

3. The attempt at a solution

I know how to calculate if their is tangential + radial acceleration but If any one could explain why there would or would not be tangential acceleration at the top and bottom point of the swing that would be very helpful because I am not sure. I am leaning towards using just the force of gravity on the ball for my final answer.

Last edited: Sep 27, 2009
2. Sep 28, 2009

### tiny-tim

Hi synergix!

From the symmetry, the speed must be at a minimum or maximum at the top or bottom, so the tangential acceleration will be zero.

3. Sep 28, 2009

### synergix

Thank you very much!! Tiny Tim :) But their would be tangential acceleration up until the instant it reached the top or bottom right?

4. Sep 28, 2009

Yup!