# Need The sum of time to calculate speed

1. Jun 8, 2004

### Tumbleweed

To all
Don't you need The sum of time to calculate speed.
This is the question in my book

A horizontal force of 280 N is exerted on a 2.0 kg discus as it rotated uniformly in a horizontal circle (at arms length) of radius 1.00 m. Calculate the speed of the discus.

I am not he smartest person around but I just for the life of me can not figure how to get the time. am I suppost to assume it.

Thanks
tumbleweed

Last edited by a moderator: Mar 7, 2013
2. Jun 8, 2004

### AKG

As far as I can tell, the discus is undergoing uniform circular motion.

$$F_{net} = F_{centripetal} = \frac{Mv^2}{R}$$

You know all the values except v for which you need to solve.

3. Jun 8, 2004

### Tumbleweed

speed

Thanks
The same formula is in the book but worded diff
That helped alot
This is my first physics class of many and I can now see it will be along road.
I am taking the class on line and I can see I needed a real class.
Thanks again
Tumbleweed

4. Jun 8, 2004

### Gza

Yes, physics unlike many other classes will be quite difficult without some guidance to help you "unwire" a lifetime of mostly false intuitions about the workings of the natural world. The only advice I have is to stick with it and you will make it through with a good understanding. I never thought of my self as particularly intelligent either, but through hard work, and really thinking through the implications of the physical laws and methods i've learned, I have succeeded and made it through all my classes with A's. My advice to you for success would be the same.

5. Jun 9, 2004

### Staff: Mentor

Don't sweat it, it appears to me to be a poorly worded problem. I also would have guessed the force was a torqure accelerating the disk, not the centripedal force on it.