## Momentum & Kinetic Energy MC *quick*

 Quote by castro94 I agree , i just used the simplified version of newtons law of motion. but from this it will still follow that both balls will gain the same velocity
That is only true for the special case of gravity, where the force happens to be proportional to the mass (so $mg = ma$ simplifies to $g = a$). Spring forces are independent of the mass of the object ($0.5 k x^2 = m a$), and are only dependent on the compression of the spring, so the resulting acceleration is indeed smaller, for the more massive object.

 The problem clearly asked for the kinectic energy " immediatly after the spring is relesed " . which means that we are not talking about any acceleration process. The ball with higher mass has a higher inertia ,it resist the "push" from the string with a greater force , from this follows that the spring will have to "provide " more energy to this ball in order to go to its normal "resting" state " .Immediatly after the spring is released , both balls will have been "pushed" with the same velocity , but the one with more mass will have "gained" more energy.

 Quote by castro94 The problem clearly asked for the kinectic energy " immediatly after the spring is relesed " . which means that we are not talking about any acceleration process. The ball with higher mass has a higher inertia ,it resist the "push" from the string with a greater force
The 'push' is the force from the spring, and force implies acceleration.

 Immediatly after the spring is released , both balls will have been "pushed" with the same velocity , but the one with more mass will have "gained" more energy.
A ball cannot be 'pushed' with a velocity. It needs an initial force to induce that velocity.
These forces can be different for different bodies and still induce the same acceleration(without which there is no velocity as the ball starts from rest)