Calculating Coefficient of Friction for a Coin on a Turntable

[atmega-ist]

I've got the answer to the problem but I'm one decimal place off from the back of the book and am suspecting a typo (no, lol... not that presumptuous...) the reason for the suspicion is that there's a zero after the answer where the units would go but this question is asking for a coefficient of friction so, of course, there should be no units... I'm just wondering if that zero was somehow misplaced in printing/formatting... I could be completely missing something though.

Homework Statement

A coin placed 30.0cm from the center of a rotating, horizontal turntable slips when its speed is 50.0cm/s. What is the coefficient of static friction between the coin and turntable?

Homework Equations

$$\mu_{s}=\frac{v^{2}}{gr}$$

$$\mu_{s}=\frac{.05m/s^{2}}{(9.81m/s^{2})*.03m/s^{2}}$$

$$\mu_{s}=.0085$$

The Attempt at a Solution

The book states ".085 0"

Is my solution correct or am I missing something?

Thanks!

 

[hage567]

I've got the answer to the problem but I'm one decimal place off from the back of the book and am suspecting a typo (no, lol... not that presumptuous...) the reason for the suspicion is that there's a zero after the answer where the units would go but this question is asking for a coefficient of friction so, of course, there should be no units... I'm just wondering if that zero was somehow misplaced in printing/formatting... I could be completely missing something though.

Homework Statement

A coin placed 30.0cm from the center of a rotating, horizontal turntable slips when its speed is 50.0cm/s. What is the coefficient of static friction between the coin and turntable?

Homework Equations

$$\mu_{s}=\frac{v^{2}}{gr}$$

$$\mu_{s}=\frac{.05m/s^{2}}{(9.81m/s^{2})*.03m/s^{2}}$$

$$\mu_{s}=.0085$$

The Attempt at a Solution

The book states ".085 0"

Is my solution correct or am I missing something?

Thanks!

You didn't convert from cm to meters correctly. The units aren't written properly, either. Is that just a typing error on your part?

 

[atmega-ist]

You didn't convert from cm to meters correctly.

I have no words...

You're exactly right. Two semesters of chemistry with EVERYTHING in mm and mL started a pretty bad habit of glossing over conversions.

The units aren't written properly, either. Is that just a typing error on your part?

Sure is. I think I got a bit carried away with the ol' CTRL+V.

Thanks so much for the second look (a.k.a. "smack-in-the-back-of-the-head").

Lol... Apologies for taking up server space for this one

 

[hage567]

Don't worry, I think we've all been there!

 

[rwisz]

Your solution appears to be correct. The coefficient of static friction is a dimensionless quantity, so there should be no units attached to it. It is possible that there was a typo in the book, or the zero could have been added in error during the printing process. It is always a good idea to double check your calculations and make sure you have the correct units, but in this case it seems like your solution is correct.