Energy

[Turkish]

Hi all,

I am sure someone can answer these rather easily as its been quite some time since the last time I took a Physics course (prolly 7 years ago in college).

I am wondering if there's a way to produce energy from force applied to a certain object? For example applying a pressure on a certain object alternatively millions of times in a minute?

Thanks.

 

[WildHorse]

wouldn't you simply convert the force to another form, like friction heat or ripple waves or something? (Conservation of energy/mass)

So energy wouldn't be produced, merely shifted from one form to another. Since any conversion wouldn't be perfectly efficient, I guess the best you could hope for would be to convert one form (your "force") to 2 other forms, say maybe convert the force of centrifugal motion into a linear motion plus heat energy lost from inefficiency, etc. There'd be lots & lots of variations on that.

If your"force" was gravitational or magnetic, then I'd have to think awhile before commenting.

You might consider the force of sunlight upon a leaf.

Photons must have a frequency (like your "alternatively millions of times in a minute") make a physical pressure pressing upon the leaf. The chlorophyl catalyzes some of the energy toward the plant's living processes like sap circulation, turning toward the light, etc., and some energy into growth of the physical structure. The plant structure is a form of potential energy to be released when the plant someday decays and decomposes.

 

[firewolfsm]

Depends on what you're applying force to, if you're squeezing a rock, you won't get much. You could use friction, create heat, and inefficiently convert that to energy.

 

[Biftheunderstudy]

Sounds like you need a piezo-electric crystal. Apply a voltage to it and it expands, AC voltage makes it vibrate.
The reverse is also true, applying pressure produces a voltage. Vibrating the crystal can create an AC voltage.

 

[PowerEngineer]

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

 

[WildHorse]

PowerEngineer,

Never knew that. Good to learn that. Thank you.

 

[PolymerTim]

Originally posted by: PowerEngineer

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

Hey, I remember that from my high school physics class. It related to work, which I guess is synonymous with energy. Work = Force * Distance so if there is no change in position then no work is done. My teacher used to joke with us that no matter how hard you pressed against a wall, if it didn't move then you weren't doing any work.

Wiki Link

 

[BrownTown]

Originally posted by: PolymerTim

Originally posted by: PowerEngineer

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

Hey, I remember that from my high school physics class. It related to work, which I guess is synonymous with energy. Work = Force * Distance so if there is no change in position then no work is done. My teacher used to joke with us that no matter how hard you pressed against a wall, if it didn't move then you weren't doing any work.

Wiki Link

Just FWIW concerning the pushing on a wall example, the reason a person can expend a large amount of energy pushing against a wall is because our muscles are not fully efficient and require energy to apply a force whether or not they are actually doing any work against an object, some animals (for example clams) have muscles that do not have this restriction, this is how a clam can apply a large force to keep its shell closed without burning any energy to do so.

This actually goes to what I see as one of the largest areas of mistakes people make when looking at units in relation to energy. Its how alot of people come up with "perpetual motion" machines. People tend to look at a LARGE quantity that is related to energy and think that this can generate a huge amount of energy, however you have to look at the equations. A huge force over a tiny distance does very little work, a huge voltage at a tiny current also supplies very little energy (see people making this mistake alot as an electrical engineer).

 

[Turkish]

Originally posted by: PowerEngineer

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

Actually this is kinda what I am digging into. If one were to apply force to pistons to move them, is it easy to produce energy from these pistons' movement (or maybe friction)?

 

[Cogman]

It really depends on what type of energy you are talking about. Kinetic energy is defined as F*d. So alternating the direction of the force would result in no net kinetic energy. However, if you are going for electrical or thermal energy, You only need to add friction or a coil of wires. Of course, only thermal will result in a + net energy gain, the electric would not be positive (but would be alternating which is very easy to manipulate into a positive energy).

 

[PolymerTim]

Originally posted by: BrownTown

Originally posted by: PolymerTim

Originally posted by: PowerEngineer

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

Hey, I remember that from my high school physics class. It related to work, which I guess is synonymous with energy. Work = Force * Distance so if there is no change in position then no work is done. My teacher used to joke with us that no matter how hard you pressed against a wall, if it didn't move then you weren't doing any work.

Wiki Link

Just FWIW concerning the pushing on a wall example, the reason a person can expend a large amount of energy pushing against a wall is because our muscles are not fully efficient and require energy to apply a force whether or not they are actually doing any work against an object, some animals (for example clams) have muscles that do not have this restriction, this is how a clam can apply a large force to keep its shell closed without burning any energy to do so.

This actually goes to what I see as one of the largest areas of mistakes people make when looking at units in relation to energy. Its how alot of people come up with "perpetual motion" machines. People tend to look at a LARGE quantity that is related to energy and think that this can generate a huge amount of energy, however you have to look at the equations. A huge force over a tiny distance does very little work, a huge voltage at a tiny current also supplies very little energy (see people making this mistake alot as an electrical engineer).

Hehe, you caught me when I was in a hurry. I guess I didn't complete that last sentence and it should be "if it didn't move then you weren't doing any work on the wall." There is plenty of work going on inside your body. I didn't know about the clams BTW; good illustration. I've seen a lot of similar mistakes as well where energy changes from one form to another and people seem to think it is created out of or disappears into thin air.

Actually, I think that is Cogman's point. There is already energy in moving pistons. The question is what kind of energy do you want, how you convert it, and the efficiency involved in the conversion.

 

[silverpig]

Originally posted by: BrownTown

Originally posted by: PolymerTim

Originally posted by: PowerEngineer

One point you don't want to forget is that energy is produced (or consumed) by moving an object in the direction of a force (or in opposition to it). Force applied to an object that does not move (or change in some way) will not produce or consume energy. As an example, your keyboard is experiencing a force on its underside couteracting the pull of gravity. That force on your unmoving keyboard neither produces or consumes energy.

Hey, I remember that from my high school physics class. It related to work, which I guess is synonymous with energy. Work = Force * Distance so if there is no change in position then no work is done. My teacher used to joke with us that no matter how hard you pressed against a wall, if it didn't move then you weren't doing any work.

Wiki Link

Just FWIW concerning the pushing on a wall example, the reason a person can expend a large amount of energy pushing against a wall is because our muscles are not fully efficient and require energy to apply a force whether or not they are actually doing any work against an object, some animals (for example clams) have muscles that do not have this restriction, this is how a clam can apply a large force to keep its shell closed without burning any energy to do so.

This actually goes to what I see as one of the largest areas of mistakes people make when looking at units in relation to energy. Its how alot of people come up with "perpetual motion" machines. People tend to look at a LARGE quantity that is related to energy and think that this can generate a huge amount of energy, however you have to look at the equations. A huge force over a tiny distance does very little work, a huge voltage at a tiny current also supplies very little energy (see people making this mistake alot as an electrical engineer).

I always hated the W = Fxd equation. I much prefer W = delta(E).

And when you push on a wall you most certainly are doing work, you're just not doing it on the wall. You are burning energy after all 🙂

 

[Cogman]

...a huge voltage at a tiny current also supplies very little energy (see people making this mistake alot as an electrical engineer).

QFT!!!

My goodness, I can't count the number of times I have heard statements like "Europe uses high voltage electricity then the US does, therefore it is more dangerous".

I feel like saying, "Oh, but they only use 220 Volts, I get shocked with an excess of 10,000 volts pretty regularly" Then when you explain to them that static electricity operates at high voltages they look at you in disbelief.


Anyways, sorry, Just need to stand of the soup box for a bit 😀