00:01
Okay, here's the sun in the middle and the earth is going in orbit around the sun like this in a circular form and the circle has radius 93 million miles.
00:13
Now i want to work out the angle the earth turns through in one day.
00:20
Let's assume then the earth moves this way and ends up here in one day.
00:27
I want to find this angle, theta.
00:29
Well, theta, in one complete year, it does one revolution, and one revolution is 2 pi radians.
00:44
And one year is 365 days.
00:49
So in one day, just divide by 365, and we get the angle the earth moves through.
00:56
How i work out on a calculator? so 2 pi divided by 365 and i get 0 .01724 radiance.
01:13
So we'll say 0 .0172 correct to 3 .sf.
01:23
That's the first one.
01:25
Part a.
01:31
Now part b, i want to work out the angular speed of the earth.
01:38
What we need do is divide the angle it turns through in a year, which is 2 pi radians.
01:49
In other words, this angle here...