00:01
Let's do some practice problems on calculating density of regular objects, unknown substances, and irregular objects.
00:12
So density is mass divided by volume.
00:17
That's our formula.
00:18
Volume can be calculated in two ways.
00:20
It's either length times width times height, or we can calculate volume of a liquid, and that's your volume final minus, your volume.
00:32
To get your final volume or your volume of your object.
00:38
So practice problem number one.
00:41
We are going to say that the mass of our object is 11 .64 grams.
00:51
We need to calculate volume.
00:54
So we have our length, which is 2 .2 centimeters.
01:01
Our width is 1 .7 centimeters.
01:05
And our height, which is 2 .4 centimeters.
01:09
So for volume, we multiply them together using our formula at the top to give us a volume of 8 .9 centimeters cubed.
01:23
Make sure you carry your units with you.
01:27
Then we go ahead and plug our numbers in, so our mass 11 .64 grams divided by 8 .4 .4 .5 .8 .5 .5.
01:37
And the density of our object is 1 .31 grams per centimeter cubed.
01:45
Our second practice problem using density is mass over volume.
01:53
Our mass of this one is 18 .38 grams and our volume we need to calculate.
02:04
So our length is 12 .6 millimeters.
02:11
Our width is going to be 7 .4 centimeters.
02:24
And our height is 0 .014 meters.
02:30
So we need to do some conversion here first.
02:33
So this one is equal to 1 .26 centimeters.
02:38
And this one over here, is going to be equal to 1 .4 centimeters.
02:46
So now that we have everything in centimeters, now we can multiply our three numbers using our volume formula, and we get 13 .1 centimeters cubed, plugging everything into the density formula, 18 .38 grams divided by 13 .1 centimeters cubed, and our density of our unknown object is 1 .40 grams per centimeter cute.
03:20
Our third, i'll rewrite our formula for us since i moved our screen, is still the same.
03:34
Density equals mass divided by volume.
03:36
Our mass is 17 .92 grams, and we'll need to calculate volume.
03:46
But we'll need to do volume final minus volume initial for this one.
03:54
And our v final was 57 .9 milliliters.
04:05
And our v initial is 23 .6 millimeters.
04:10
Once we subtract, our volume total is 34 .3 millimeters.
04:18
We can go ahead and plug that in, divided by 34 .3 milliliters...