Zero Momentum?
Classical Mechanics
Level
2
Take for example an object that supposedly has zero mechanical energy. Does this also mean that it will also have zero linear momentum? Always?
No, not always
Yes, always
No because it can have negative kinetic energy and negative velocity
Yes because kinetic energy is zero so velocity is zero.
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1 solution
We can easily cross out most of the options because kinetic energy is never negative. Even if the velocity is negative, the object would still have positive kinetic energy because it is moving.
However, zero mechanical energy does not mean that potential energy and kinetic energy have to be zero. The kinetic energy can be any value, for example, 200 J. Then the potential energy would have to be - 200 J in order for the resulting mechanical energy to be zero. And this is possible.
Take gravitational energy for example. It can be negative or positive depending on the reference frame of your choice. So this essentially means that momentum will not be zero if mechanical energy is zero because kinetic energy does not necessarily have to be zero.