Use the formula KE = (1/2) mv2. (Kinetic energy = 1/2 x mass x speed squared.) Replace the values you know, and solve the resulting equation for the speed.
divide the energy by the mass - then take the square root
By multiplying the mass times the velocity squared.
The mass will be equal to the kinetic energy divided by the velocity squared. m=2(KE)/(v2). This is from the basic equation KE=1/2mv2.
Kinetic energy = (1/2) x (mass) x (velocity)2