Internal Energy of Falling Stone in Vacuum: Is ΔU Zero?

In summary: In the case of a stone falling under gravity in a vacuum, its internal energy will not change as there is no external force acting on it. Therefore, the change in internal energy (ΔU) will be zero. However, if the stone is falling in a strong gravitational field, such as near a neutron star or black hole, its internal energy could potentially change due to tidal effects. In summary, when a stone falls under gravity in a vacuum, its internal energy remains constant as there is no external force acting on it. However, in a strong gravitational field, its internal energy could potentially change due to tidal effects.
  • #1
ketz
6
0
A stone is falling under gravity in a vacuum. Is its internal energy increasing?

Well, since internal energy(Microscopic level) is defined as the energy associated with molecules(Sum of kinetic energy and potential energy of the molecules). The molecules inside the ball will not gain any K.E or P.E since it is not being affected. Hence, I think ΔU will be zero! Is it correct??
 
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  • #2
ketz said:
A stone is falling under gravity in a vacuum. Is its internal energy increasing?

Well, since internal energy(Microscopic level) is defined as the energy associated with molecules(Sum of kinetic energy and potential energy of the molecules). The molecules inside the ball will not gain any K.E or P.E since it is not being affected. Hence, I think ΔU will be zero! Is it correct??
Measurement of energy depends on the frame of reference in which the measurement is made. If the "internal energy" of a quantity of matter is defined as the potential and kinetic energy of molecules as measured in the frame of reference of the centre of mass of that quantity of matter, then, ignoring any tidal effects, you are correct.

If the stone is falling in the gravitational field that has a significant gradient - eg. close to a neutron star or black hole, the stone could stretch (one end accelerating faster than the other), in which case its internal energy could change.

AM
 

Related to Internal Energy of Falling Stone in Vacuum: Is ΔU Zero?

1. What is internal energy in the context of a falling stone in a vacuum?

Internal energy refers to the total energy of all the particles within a system. In the case of a falling stone in a vacuum, the internal energy would include the kinetic energy of the stone as well as any potential energy it may possess due to its position in the Earth's gravitational field.

2. Why is the internal energy of a falling stone in a vacuum often considered to be zero?

In a vacuum, there is no air resistance or other external forces acting on the falling stone, so it is not losing or gaining any energy from its surroundings. Additionally, as the stone falls, its potential energy decreases while its kinetic energy increases, resulting in a constant total energy. Therefore, the change in internal energy (ΔU) is zero.

3. Can the internal energy of a falling stone in a vacuum ever be non-zero?

Technically, yes. If there is any external force acting on the falling stone, such as air resistance or a change in the Earth's gravitational field, then the internal energy would not be zero. However, in a vacuum with no external forces, the internal energy will always be considered zero.

4. How does the concept of internal energy apply to a falling stone in a vacuum?

The concept of internal energy is important when considering the conservation of energy in a falling stone in a vacuum. While the internal energy itself may be zero, the total energy (kinetic + potential) remains constant, demonstrating the law of conservation of energy.

5. Why is it useful to calculate the internal energy of a falling stone in a vacuum?

Calculating the internal energy can help us understand and analyze the behavior of the falling stone. It allows us to see how the potential and kinetic energies are changing throughout the fall, and it also helps to verify the law of conservation of energy. Additionally, it can be used to make predictions about the motion of the stone and its final state when it reaches the ground.

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