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?

 

[M98Ranger]

A) If the kinetic energy of a particle is zero, it means that the particle is not moving. In this case, its momentum would also be zero. This is because momentum is a measure of an object's motion, and if there is no motion, there is no momentum. This can also be understood by looking at the equation for momentum, which is mass multiplied by velocity. If the velocity is zero, the momentum must also be zero.

B) No, if the total energy of a particle is zero, it does not necessarily mean that its momentum is also zero. This is because there are different forms of energy, such as kinetic energy and potential energy. The total energy of a particle is the sum of all these different forms of energy. So even if the kinetic energy is zero, there could still be potential energy present, which would contribute to the total energy. Therefore, the momentum of the particle would not necessarily be zero. For example, a particle can have zero kinetic energy but still have potential energy due to its position in a gravitational field. In this case, the particle would still have momentum due to its potential energy.