# Finding Mass of a Sphere

1. Mar 21, 2010

### Ripcurl

1. The problem statement, all variables and given/known data
A sphere of metal has a radius of 5.3 cm and a density of 8.15 g/cm3. What is the mass of the sphere? Answer in units of g.

2. Relevant equations
Density=mass/volume

Volume of a sphere=4/3лr^3

3. The attempt at a solution
I found the volume by multiplying 4/3 by л and 5.3 squared. I got 66.1850323. I plugged this into the formula for density, manipulated it to get mass by itself and got 539.4118513. This answer seems really unreasonable. I think I need to do some conversions but I'm not sure what to convert. I think I need to convert the radius to meters but the density is in grams/cm cubed and I need to answer in units of grams.

Last edited: Mar 21, 2010
2. Mar 21, 2010

### Kabbotta

Mass = density times volume

First, volume of a sphere is 4/3$\pi$r^3.

Next, don't convert anything you've been given the right units for what you've been asked for. Produce a volume for the sphere in terms of cm^3, then

$cm^3$ * $\frac{g.}{cm^3}$ = $g.$

Last edited by a moderator: Feb 26, 2015
3. Mar 21, 2010

### Ripcurl

So you're saying find the volume. I got 623.6145193 cm^3. Then I multiply that by the density (8.15) to get the mass. I get 5082.458333. That doesn't seem right. XD

4. Mar 21, 2010

### Ripcurl

But it is. Wow. You're amazing! Thanks! XD

5. Mar 21, 2010

### Kabbotta

Remember that the equation of finding the mass of a sphere is

Mass = density times volume

Last edited by a moderator: Feb 26, 2015