what formula do i use :)
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Well, without knowing anything much you know that it will probably be proportional to the mass of the earth, proportional to the mass of the moon, and inversely proportional to the square of the distance between them. So something like this:
1. F ∝ M • m / D²
However, F is in Newtons or kg•m/s² and the right side of the above is in kg²/m². Odds are, when you see that, there is at least one 'constant' involved to match up the left side's units with right side's units of force. Whatever it is, its units are m³/(kg•s²). Turns out this is called G, the constant of universal gravitation and its value is 6.673•10^-11 m³/kg•s², with units as expected.
So the full equation is:
2. F = G • M • m / D²
You just need some values. Google can provide them and this works on the google search box:
(gravitational constant)*(earth mass)*(mass of moon)/(384400 km)^2
To get about 1.9857•10^20 Newtons.
1. F ∝ M • m / D²
However, F is in Newtons or kg•m/s² and the right side of the above is in kg²/m². Odds are, when you see that, there is at least one 'constant' involved to match up the left side's units with right side's units of force. Whatever it is, its units are m³/(kg•s²). Turns out this is called G, the constant of universal gravitation and its value is 6.673•10^-11 m³/kg•s², with units as expected.
So the full equation is:
2. F = G • M • m / D²
You just need some values. Google can provide them and this works on the google search box:
(gravitational constant)*(earth mass)*(mass of moon)/(384400 km)^2
To get about 1.9857•10^20 Newtons.