# Physics Problem need help

1. Sep 22, 2011

### joecocobo

Need Help Now

A string wound on the rim of a wheel 20 cm in diameter is pulled out at a rate of 75 cm/s. Through how many revolutions will the wheel have turned by the time that 9.0m of string has been unwound? Also how long did it take?

I really need help with this. If you post, please show all work so I can learn how to do this type of problem.

2. Sep 22, 2011

### Staff: Mentor

Re: Need Help Now

joecocobo, welcome to PF.

You'll have to follow the posting template and show your attempt at working on the problem before help/hints/guidance can be offered.

3. Sep 22, 2011

### joecocobo

1. The problem statement, all variables and given/known data
A string wound on the rim of a wheel 20 cm in diameter is pulled out at a rate of 75 cm/s. Through how many revolutions will the wheel have turned by the time that 9.0m of string has been unwound? Also how long did it take?

2. Relevant equations
I don't know any equations to use

3. The attempt at a solution
I honestly don't know where to start, to even make an attempt

Last edited by a moderator: Sep 22, 2011
4. Sep 22, 2011

### DaveC426913

You may be overthinking it. For starters, separate the question into its two components. They are not related.

1] A 9.0m string is wound on the rim of a wheel 20 cm in diameter. How many times is the string wrapped around the wheel?
Do you know the relationship between the diameter of a circle and its circumference?

2] How long will a point on the string take, moving at 75cm/s, to travel 9.0m?
Do you know how to calculate time, given a distance and a velocity?

Last edited: Sep 22, 2011