Escape velocity question

I have forgotten how to work out the escape velocity of a gravitational field once the gravitational potential of the surface has been worked out, help would be appreciated.

Here is the question;

The asteroid Cere's has a mass of 7.0x10^20 Kg and a radius of 550Km

a) What is the gravitational potential at the surface of Cere's?

Which I can do and the answer came out as -8.50x10^4 JKg^-1

b) What is the min escape velocity from the surface?

Need help here

Reply 1

Stonebridge

13

The PE of the object at infinity (where it can be said to have escaped from the gravitational field of the mass) is zero.
If you know the PE on the surface (a negative value), then you would need to give it that amount of energy to get it to infinity.
If this energy is initially kinetic, then just equate the initial ½mv² of the object to this PE value.
v in this case would be the speed needed to escape.

Reply 2

TheJ0ker

OP

11

Original post by Stonebridge

The PE of the object at infinity (where it can be said to have escaped from the gravitational field of the mass) is zero.
If you know the PE on the surface (a negative value), then you would need to give it that amount of energy to get it to infinity.
If this energy is initially kinetic, then just equate the initial ½mv² of the object to this PE value.
v in this case would be the speed needed to escape.

But I don't know the mass of the escaping object, the question just asks for the minimum escape velocity so I thought I wouldn't be able to use 1/2mv^2

I don't understand how to work out the escape velocity without the mass.