Car B is traveling twice as fast as car A, but car A has three times the mass of car B. Which car has greater kinetic energy?
Kinetic energy is the energy that an object has due to the fact that it is moving. The kinetic energy of a body with mass m moving with a velocity v is give by (1/2)*m*v^2
The car B is travelling twice as fast as car A and the mass of car A is three times that of car B. If we denote the mass of car A as M and the velocity of car A as V, the mass of car B is M/3 and its velocity is 2*V
The kinetic energy of car A is (1/2)*M*V^2.
The kinetic energy of car B is (1/2)*(M/3)*(2*V)^2 = (1/2)*(M/3)*(4*V^2)
We see that the kinetic energy of car B is (4/3) that or car A. This implies that car B has a greater kinetic energy of the two cars.