Question

please help. A motorcycle stops and generates 34kcal it has a mass of 400kg. How fast is it traveling?

Answer 1

kcal is an measure of energy
It is more usual and more useful in this case to convert it to joule

Find the conversion factor and convert the kcal to joules

In stopping it has converted its initial Kinetic energy in to heat (in the brakes) so the joules 'generated' is equal to its initial KE

KE = 1/mv^2

So - you know the energy and the mass, so solve for v

Answer 2

that should be
KE = 1/2 *mv^2 (half mass * velocity squared)