Can someone carefully explain negative potential energy please?

[medemic]

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As stated... I just don't get it.

 

[sakabato93]

Well, potential energy is just a relative quantity. There is an arbitrary set point of zero, and your values are based on that.

Unless you give an example of the a situation, that is the best I can give you.

 

[mehc012]

As stated... I just don't get it.

An object has a 'negative' potential energy when it has less PE than it would at whatever you set as your zero state.

For example, if you have a rock, and you set the zero for the gravitational PE as the amt it has when it is a mile off the ground, then it will have less PE when it is sitting on the ground, and any number less than zero is negative.

 

[tynandaly]

Negative potential energy is easy to see in electrostatics. If a positive charge and a negative charge are near each other, they will have a positive potential energy because they are favored to move towards each other.

However, if BOTH charges are positive, the potential energy will be negative because there is a repulsive force. They are NOT favored to move closer to each other, they actually want to move away to get to a more stable energy state.

If potential energy is the energy which would be used to get an object to its lowest energy state (an apple back to the ground, a stretched spring back to its base, etc.), then in this case it would be negative since they want to move away from each other instead.

Hope this helps.

 

[mehc012]

Negative potential energy is easy to see in electrostatics. If a positive charge and a negative charge are near each other, they will have a positive potential energy because they are favored to move towards each other.

However, if BOTH charges are positive, the potential energy will be negative because there is a repulsive force. They are NOT favored to move closer to each other, they actually want to move away to get to a more stable energy state.

If potential energy is the energy which would be used to get an object to its lowest energy state (an apple back to the ground, a stretched spring back to its base, etc.), then in this case it would be negative since they want to move away from each other instead.

Hope this helps.

Instead of what? Those last few sentences are very unclear, and make it seem as if you mean to imply that moving away from each other makes the two charges less stable (which isn't true).

 

[Synapsis]

Negative potential energy is easy to see in electrostatics. If a positive charge and a negative charge are near each other, they will have a positive potential energy because they are favored to move towards each other.

However, if BOTH charges are positive, the potential energy will be negative because there is a repulsive force. They are NOT favored to move closer to each other, they actually want to move away to get to a more stable energy state.

If potential energy is the energy which would be used to get an object to its lowest energy state (an apple back to the ground, a stretched spring back to its base, etc.), then in this case it would be negative since they want to move away from each other instead.

Hope this helps.

You've got this mixed up.

If you have a proton and electron (the examples of positive and negative charge), the potential energy will be negative. That is, when the charges are different, the potential energy is negative. Check this with Coulomb's Law, V = kqq/r. I intentionally left out the constants in the denominator because they aren't important right now. q is the charge on the particle. If one of the q's is negative and one is positive (opposite charge example), then a negative times a positive is a negative, so potential will be negative. Since we know that opposites attract, that means a negative potential is attractive. If both of the q's are positive or both are negative (same charge example), V will be positive. That's repulsive.

 

[medemic]

You've got this mixed up.

If you have a proton and electron (the examples of positive and negative charge), the potential energy will be negative. That is, when the charges are different, the potential energy is negative. Check this with Coulomb's Law, V = kqq/r. I intentionally left out the constants in the denominator because they aren't important right now. q is the charge on the particle. If one of the q's is negative and one is positive (opposite charge example), then a negative times a positive is a negative, so potential will be negative. Since we know that opposites attract, that means a negative potential is attractive. If both of the q's are positive or both are negative (same charge example), V will be positive. That's repulsive.

I think I get it now.

 

[tynandaly]

I had it backwards, thanks Synapsis for correcting me. Using the equation U=kqq/r is the best way of looking at it.