00:01
At a certain distance away from the center of the earth, a 5 kilogram object has a weight of 3 .6 newton's.
00:07
Here i've drawn the earth and the object a certain distance away, an r distance away, in fact, with a mass m, which i have written to be equal to 5 .0 kilograms.
00:21
And the problem wants us to find the distance r.
00:25
Let's go ahead and start with newton's gravitational law, f big g.
00:30
Is equal to g m1m2 over r squared and here we're going to be trying to find the variable r fg f big g on the left this will be the weight of the mass because that is the force that the mass feels from the earth and the force that the mass feels from the earth would be what the mass itself feels like its weight is.
01:03
So the weight is 3 .6 newtons.
01:08
Actually, let's solve for this symbolically and then plug in the numbers.
01:13
So r squared, r squared will be equal to g.
01:22
M1, m2 over f big g.
01:26
I simply swapped this f big g with r squared here.
01:32
And we take the square root so that we get square root of big g m1 m2 over f g and here m1 will be the mass itself and m2 will be the mass of the earth so if we go ahead and plug all that in we will get a distance of 2 .35 times 10 to the 7 meters notice that this radius is greater than the earth's radius, so the object will be somewhere flying in the atmosphere...