# Intro Physics question

1. Sep 11, 2011

### lab-rat

2. Sep 11, 2011

### Hootenanny

Staff Emeritus
You must have some idea as to where to start. We can't help you unless you at least attempt the problem first.

3. Sep 11, 2011

### lab-rat

Well my professor hasn't given any examples yet on this and I can't find any in my textbook either. I was hoping someone could give me pointers on where to start.

4. Sep 11, 2011

### lewando

You can start by looking on the interweb for things like "measuring the diameter of a molecule".

5. Sep 11, 2011

### lab-rat

I haven't done any physics or math in over a year which is probably why I'm having trouble with pretty basic problems.

Here's my attempt:

(a) Area of slick = $\pi$r2
diameter of slick = 2x1010
volume of slick= area x thickness
volume of oil=volume of slick= 1L = 0.001m3

0.001m3=($\pi$r2
r=1261.57m
d=2523m

(b) $\rho$=M/V
V=$\pi$r3
=$\pi$(1x10-10)3
V=3.14x10-30m3
M=850kg/m3 x 3.14x10-30m3

M=2.67x10-27kg

does that make sense?

6. Sep 11, 2011

### lewando

Looks okay, too many significant digits though.

V=$(4/3)\pi$r3

7. Sep 11, 2011

### lab-rat

Thank you!

The diamete/thickness was a typo, I wrote it properly on my sheet :)

As for the significant digits, does 2.5x103m work?

8. Sep 11, 2011

### lewando

If you are using a number like 2x10-10, I think one SD would suffice.