Help physics/math

An object of mass 65.0 kg is transported to the surface of Planet X where the object's weight is measured to be 18.5 Newtons. The radius of the planet is 4x10^6 meters. What is the mass of Planet X?

Question

Help physics/math

An object of mass 65.0 kg is transported to the surface of Planet X where the object's weight is measured to be 18.5 Newtons. The radius of the planet is 4x10^6 meters. What is the mass of Planet X?

amorfide · Answer

$$F_{grav}=\frac{ Gm_{planet}m_{object} }{ r^{2} }$$
i believe this formula is correct

then you know

$$F=m_{object}g$$
so you divide by the mass of the object on both sides to get
$$g=\frac{ Gm_{planet} }{ r^{2} }$$

and you can use W=mg to work out the gravity on this planet I assume that is why they gave you these values

This is my best approach
I do not do physics though

princeharryyy · Answer

$$G=6.75 * 10^{-11} N$$

mrnood · Answer

G is not a force - it is a constant. Its units are not N

gravitational constant =

6.67408 × 10-11 m^3 kg^-1 s^-2

mrnood · Answer

@amorfide has the correct equation.

You do not need the intermediate step though

Fgrav is teh weight - which is given as 18.5N
G is the constant given above

So the only unknown in the equation is mplanet