A friend raised an observation which I thought would be easy to explain. But it seem I have a gap in my physics knowledge... An object (rigidbody) is stationary in zero gravity empty space. In the first situation we apply an impulse to its COG and its linear momentum changes, and no angular momentum change. Correct? In the second situation, same initial condition, but the same impulse is apply off center, inducing a change in angular velocity, as well as the same change in linear momentum as in the first situation. In the first situation, the impulse resulted in the object having an linear kinetic energy. In the second situation, the impulse caused the object to have the same linear kinetic energy, but also an additional rotational kinetic energy. Why aren't the total kinetic energy after the impulse the same in both situation? Thanks for answering.