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# Tag Info

## Hot answers tagged potential-energy

16 votes

### In equation (3) from lecture 7 in Leonard Susskind’s ‘Classical Mechanics’, should the derivatives be partial?

The notation is a little sloppy from a purely mathematical point of view (although common in physics) so it might be causing a little confusion. To help clarify, it might help to use different letters ...
• 50.9k
10 votes
Accepted

### Can a big mass defect make the mass negative?

If you apply no rules to the possible interactions then what you describe is possible. But the negative bound state mass can be avoided if we assume two things: A force field that has always positive ...
• 4,713
9 votes

### Why potential energy is not considered in the internal energy of diatomic molecules?

Note that potential energy is defined on a relative scale, and so we are free to chose the state which we call the zero potential energy state. Since the diatomic molecules are considered rigid, their ...
7 votes

### When is minimum potential energy in simple harmonic motion not zero?

Potential energy can always be shifted by an arbitrary constant. For a Hooke's Law spring, this means we can write $U=\frac12 k(x-x_0)^2+U_0$. For a physical example, consider a mass on a vertical ...
• 91.4k
7 votes

### When is minimum potential energy in simple harmonic motion not zero?

Energy has no absolute reference zero. The potential energy at zero displacement could be $0\,\rm J$, $1\,\rm J$, $10^9\,\rm J$, or $-10^9\,\rm J$ depending on where you set your (arbitrary) reference ...
• 26.4k
6 votes

### Why potential energy is not considered in the internal energy of diatomic molecules?

You're right - there is an additional degree of freedom from the potential energy of the bond! In fact, there is also another kinetic degree of freedom from the relative motion of atoms as they ...
• 444
6 votes

### Can a big mass defect make the mass negative?

TL;DR: No, quantum field theory does not allow this. The general situation you describe is not at all exotic, and in fact this is why we have (meta)stable bound states. What you have termed 'mass-...
• 589
3 votes

1 vote

### When an object is thrown towards the sky it starts to gain potential energy, why?

There are two ways to view the exchange of kinetic energy and potential energy. But before I do, I'd like to point out that your learning of physics will be much much easier if you drop the concept ...
• 50.2k
1 vote

### Can a big mass defect make the mass negative?

This question leads to deep insights into what constitutes a particle relative to the vacuum. If you were to have a system of particles with binding energy less than the vacuum, the universe would ...
• 973
1 vote

### Comparing Electric Potential Energy of two Charges

In the case that A and B both have the same positive charge: remember that potential energy associated with a position (it is not defined as something that requires two positions e.g. A and A') is the ...
1 vote

### Why is work done by force $+mgh$ in the situation of throwing something up?

You are right, the work applied is not necessarily equal to $mgh$. To see this, let's look at energy conservation: $$K_0+U_0+W_{\text{n.c.}}=K_f+U_f$$ where $K_0$ and $K_f$ are the initial and final ...
• 57.2k
1 vote

### Why potential energy is not considered in the internal energy of diatomic molecules?

There is intramolecular potential energy and intermolecular potential energy. The first applies to the chemical and nuclear bonds of the molecule/atom. The second applies to the potential energy ...
• 73.5k
1 vote

### In which situation the potential energy of a system is equal to its Gibbs free energy?

I can imagine situations that PES is equal to G, when we have two identities: PES = U (ideal conditions) U = G (Equilibrium or "no action" = zero Lagrangian) The potential energy surface (...

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