00:01
So in this video, we want to look at the acceleration, or the force of gravity between the earth and then the sun.
00:08
So in the problem, we get given newton's law of gravitation, where the gravitational force is equal to the gravitational constant, the mass of both of the objects, divided by the radius between them squared.
00:23
So we're going to have the radius, and then we have the mass of the earth, we can call it, and then the mass of the sun.
00:31
So we need to look up some information here about the masses and the distance.
00:35
You can look that online or maybe in the back of many textbooks.
00:39
We find that the mass of the earth is equal to 5 .97 times 10 to the 24 kilograms.
00:52
So obviously quite big.
00:54
And then the mass of the sun, we expect it to be a lot larger.
00:56
And it is 1 .99 times 10 to the 30 kilograms.
01:02
So there's an exponent of six difference here, so that means the mass of sun is about a million times the mass of the earth.
01:09
We also want to know the radius, and the orbit of the earth is an ellipse, so relative to the sun, sometimes it's closer and sometimes it's farther.
01:19
This is very exaggerated, though.
01:20
It is pretty close to circular.
01:24
So we can use as the radius, the semi -major axis, sma.
01:29
And when you look at that, we see that the semi -major axis of the orbit of the earth around the sun is, so that would be our radius we'll use, 147 times 10 to the 6 kilometers, and we need to deal with the kilometers later.
01:47
So this is kind of the average between the middle point of the earth and the sun, which would give us a good approximation.
01:54
And it's, like i said, it's very close to circular, so this works fine...