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# Under what circumstances (if any) is a golf ball's kinetic energy negative? (ball is in a hole)Its rest energy?

I’m looking at the formula and I don’t think KE can ever be negative. I mean, the mass is never negative and the velocity is squared. Am I forgetting something?
Also, what do they mean by rest energy? The question said in the beginning: “The PE of a golf ball in a hole is negative with respect to the ground.” Therefore, they don’t mean rest = potential, right? I’m so confused!!!

1. You are correct. Kinetic energy can’t be negative.
And yes, they are apparently using rest energy to mean potential energy–an unusual usage, but clear under the circumstances.
Potential energy is always measured relative to an arbitrary reference point. A ball in a hole has less potential energy than a ball on the ground outside of the hole. So if the ground is taken to be zero, the ball in the hole has negative potential energy.

2. What they mean is that if the ground level has zero potential energy, you must give the ball energy to bring it up to ground level, therefore its potential energy is negative.
Its kinetic energy is never negative.
EDIT: Another answer says that energy can never be negative, but this not correct. This is not really relevant to this problem, but bound states are typically thought of as having negative total energy, because we can imagine giving energy to something (like an electron) to free it from being bound to an atom. Typically in those cases potential energy is taken as zero at infinite separation, so if the particle is bound it has less energy than zero, making it negative. If its positive kinetic energy is greater than its negative potential energy, it is not bound.

3. Energy can not be negative, whatever is the form.
I agree acceleration can be negative, and so is work. But energy can never be negative.
teddy boy

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