Need an aerodynamics guru to help me out! Please!

[Edge 540]

Correction- mechanical energy is the potential and kinetic energy of the object, not just kinetic. ME = ability to do work.
This can be from potential energy
- gravitational, elastic or otherwise
-OR Kinetic.

[Wojcigitty]

Where else would the energy go, but to create heat? Also, your energy should be in Joules, not Newtons. Newtons are a measurement of force. Potential Energy = mgh = kilograms * meters per second per second * meters = Newtons * meters traveled. What it comes down to is that the body has 360 less Joules of energy in kinetic form at the end of the fall than it did in potential form at the beginning of the fall. The only place for that energy to go is to create heat, be it in the body or in the atmosphere.

[niccolo98]

So your saying, that when a body falls, the only loss of energy is due to heat?

[Vic3D]

There is no loss of energy. Google Law of conservation of energy.

[Wojcigitty]

	Quote: Originally Posted by niccolo98
	So your saying, that when a body falls, the only loss of energy is due to heat?

Maybe. There is no loss of energy, as Vic said, it's simply changed from one form to another (kinetic to heat, potential to kinetic, etc).

In this case, the problem states that the potential energy is converted to kinetic energy (falling motion). Some of this kinetic energy is lost, and, because there's nothing else to slow it down, you must assume it's converted to heat.

[CRG]

The kinetic energy is not lost in conversion to heat. The 'loss' in kinetic energy is due to the atmosphere slowing the object, and it is the motion through the atmosphere that is creating the heat.

CG.

	Quote: Originally Posted by Wojcigitty
	Maybe. There is no loss of energy, as Vic said, it's simply changed from one form to another (kinetic to heat, potential to kinetic, etc). In this case, the problem states that the potential energy is converted to kinetic energy (falling motion). Some of this kinetic energy is lost, and, because there's nothing else to slow it down, you must assume it's converted to heat.

[TheTank]

	Quote: Originally Posted by CRG
	The 'loss' in kinetic energy is due to the atmosphere slowing the object, and it is the motion through the atmosphere that is creating the heat. CG.

The object will not begin to slow, as it it was dropped, and was accelerating. Only after accelerating to terminal velocity, the object would then maintain velocity, but not slow it down. Now, if it was dropped from say 30,000 feet, the density of the atmosphere as the terminal speeds would change through different levels of the atmosphere, and would product a slowing affect.

As the others said, there is no loss of energy, the form just changes. In this case, to entropy, or heat.

[TheTank]

After looking at your post again, I think I misinterpreted what you were saying, you meant the slowing of the acceleration, not the actual slowing of the object. In that case, yes, acceleration lessens as it reaches terminal velocity, and that energy is lost to heat. (Note to self, read more carefully next time!!! )

[niccolo98]

Sorry, I meant to say converted. So, again what your saying is, tat when an object falls, the only conversion of energy, is that of the kinetic into thermal??
seems odd to me.
nick

[Wojcigitty]

	Quote: Originally Posted by niccolo98
	Sorry, I meant to say converted. So, again what your saying is, tat when an object falls, the only conversion of energy, is that of the kinetic into thermal?? seems odd to me. nick

Maybe. But in this case, you are told that the potential energy is converted to thermal and kinetic, nothing else. Since you know how much is kinetic, you must assume the rest is thermal.

[somethnextra]

The only energy tradeoffs in this case would be between thermal, mechanical, and potential. There are other kinds of energy (chemical, magnetic, electrical, etc...) but I wouldn't think they'd be applicable here unless your ball is a ball of plutonium. Also, almost ALL physics problems (especially one like this) neglect air friction. It's an assumption inherent to the problem for a course like this.

[prizzy]

The math is correct, I think you professor wrote the question badly. The engergy is lost to friction of course, but it will not manifest itself is totally heat. Think about a large draggy object like a parachute, it is losing a ton of KE to drag, with no significant real world heat gain. He would have been better to write it saying what amount of energy is lost, period. Unless he gave you the cross sectional area, then it gets funner.