Answer: The kinetic energy of Derek's bike is 384.
To find the kinetic energy of an object, we need to know the mass and the velocity of the object. Both of those are already given in the problem. So we can simply use the formula.
The formula for kinetic energy is KE =0.5(m)v^2. All we need to do is input the know variables and evaluate.
KE = 0.5 (12) (8^2)
KE = 0.5(12)(64)
KE = 384