Asteroid Speed: Calculating with Kinetic Energy

[ahrog]

Homework Statement

A 4.50 x 10^4 kg asteroid has 6.20 x 10^12 J of kinetic energy. What is the speed of that asteroid?

Homework Equations

W=Fd
P=W/T
P=Fv

The Attempt at a Solution

V=p/f
V=(6.2 x 10^12)/((4.50 x 10^4 kg)(9.8)
V=1.41 x 10^7 m/s

I am wondering about the gravity part though. Normally, for weight it is on earth, so 9.8 works. But if the asteroid is in space, then can I still use 9.8?

 

[Carid]

KineticEnergy = 0.5 * mass * velocity * velocity

no gravity involved