# How to calculate the speed of an object attached to a string

1. Dec 5, 2017

### aron silvester

1. The problem statement, all variables and given/known data
The question and the known/given variables are on the image in part 3. The question says that a 20-g bead is attached to a light 120 cm-long string. Now in my mind the bead will travel in a circular path if it is pushed really hard. So Isn't the length of the string, 120 cm, the radius of the circle? In my work, I had to solve for the radius. I found a solution online and this is their work. The correct answer is 1.1 m/s.

2. Relevant equations
It's in part 3 in the image.

3. The attempt at a solution
https://myhpu-my.sharepoint.com/per...R0RpKa0PGg&e=cf5a0f07109f401fb33a7a681a70fc4a

2. Dec 5, 2017

### Staff: Mentor

The bead rotates in 3 D while keeping its height. It is not a typical pendulum. The r in the lower left part of the image is the horizontal separation of the object - the radius of the horizontal motion. It is a bit confusing that the same variable name is used again.

Edit: Picture for future reference:

Last edited: Dec 5, 2017
3. Dec 5, 2017

### aron silvester

Wow, it makes so much sense now! Thanks!!!!