How would the kinetic energy of a 12,000 kg train compare with the kinetic energy of a 900 kg compact car if both were traveling at the same speed?
a. the trains kinetic energy would be equal to the cars kinetic energy.
b. the trains kinetic energy would be greater than the cards kinetic energy.
c. the trains kinetic energy would be less than the cars kinetic energy.

Kinetic energy of any object is (1/2) x (object's mass) x (object's speed)².

If the speeds are the same, you can see from this formula that the bigger
mass has the bigger kinetic energy, in direct proportion.

The train has (12,000/900) = 13 and 1/3 times as much kinetic energy as the car has.

The correct choice is 'B'.

(In the real world, 12,000 kg might only cover the locomotive.)

The answer is a) carbon-12