Potential Energy: Energy Input & Output

In summary, potential energy is defined as the energy of a system at a given configuration, but the exact value is arbitrary as long as the differences in potential energy are considered. The sign of a change in potential energy indicates whether energy was added or removed from the system.
  • #1
phymathlover
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Can we say that positive potential energy means energy is given out by the system when it is brought to the present state of configuration and negative potential energy implies that energy needs to be provided to the system to achieve the present state?
 
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  • #2
A value of potential energy doesn't really mean anything, only differences in potential energy matter.

For example, the pot. energy of a system of two planets with masses ##M_{1}## and ##M_{2}## is usually defined as

##V(r)=-G\frac{M_{1}M_{2}}{r}## ,

where ##G## is the gravitational constant and ##r## is the separation between the planets. The definition makes the potential energy zero at infinite separation and negative at any finite separation. However, if we instead use the definition

##V(r)=-G\frac{M_{1}M_{2}}{r}+V_{0}## ,

where ##V_{0}## is any constant with dimensions of energy, the model predicts exactly the same physics. Changing potential energies by an additive constant doesn't change anything.
 
  • #3
Hilbert2 beat me to it, but here is my reply anyway.

The zero of energy is purely arbitrary. For example, you can put the zero of potential gravitational energy at the surface of the Earth, at the center of the Earth, or on the Moon. The same object in the same state can thus have positive, negative, or zero potential energy.

The sign of a change in potential energy tells you something about what happend. If the sign is positive, then energy was put into the system to bring it to its current state. If it is negative, energy was taken out. Using again the example of gravity, if I lift an object from the floor, it gains potential energy (positive sign for the change). If I let it drop, it will lose potential energy (negative sign for the change) as it gets converted to kinetic energy.
 
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FAQ: Potential Energy: Energy Input & Output

What is potential energy and how is it related to energy input and output?

Potential energy is a form of energy that an object possesses due to its position or configuration. It is related to energy input and output because it represents the amount of energy that can potentially be transformed into other forms of energy.

How is potential energy calculated?

The formula for calculating potential energy is PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object.

What is the difference between gravitational potential energy and elastic potential energy?

Gravitational potential energy is the energy an object has due to its position in a gravitational field, while elastic potential energy is the energy stored in an object when it is stretched or compressed.

Can potential energy be converted into other forms of energy?

Yes, potential energy can be converted into kinetic energy, thermal energy, or any other form of energy through various processes such as chemical reactions, mechanical work, or heat transfer.

How does potential energy contribute to the Law of Conservation of Energy?

The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed from one form to another. Potential energy plays a crucial role in this law as it represents the stored energy that can be transformed into other forms of energy.

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