Kinetic Energy and Momentum

[steph01mcd]

I need a little help.

A) If the kinetic energy of a particle is zero, what is its momentum?Explain.

B) If the total energy of a particle is zero, is its momentum nexcessarily zero? Explain.

[HallsofIvy]

The kinetic energy is (1/2)m v2. If the kinetic energy is 0, what does that tell you about v? (or about m!) What is the momentum in that case?


Total energy includes both kinetic and potential energy. Kinetic energy is never negative (since v2 is never negative) but since potential energy is always relative to some reference point, potential energy can be negative. For example if we take the potential energy to be 0 at the top of a cliff of height h, at the bottom the potential energy of a mass m is -mgh. Can you think of an example in which kinetic and potential energies cancel?