If i push my hand down on a desk (without moving the desk) do i do any work?

Question

If work is the change in energy, then clearly i am doing work because i am losing energy as i push down on the desk. However, if work is also force multiplied by distance, then i am doing no work because i have not moved the desk

Answer 1

You are applying force, but you are not doing any work. Work, by its very definition, requires motion. You are applying potential energy, work is not done until it is converted into kinetic energy.

Answer 2

Of course you are doing work, even though the desk is not moving. That just means that the amount of energy that you've expended is NOT sufficient to overcome the electromagnetic forces holding the molecules of the floor together.

Most people learn in school about the work function as force times distance, but that's an idealized situation where there is (1) NO friction, and (2) NO obstables in the direction of the force.

Obviously in the real world, if I were to try to push an object along on the ground, the actual work done has to be (1) work done to overcome frictional forces, plus (2) work done moving the object from position A to position B.

So if you were pushing down on a desk, and the desk sits on a concrete floor, then the answer to the question "how much work will I do?" does not depend on the distance the desk moves. That's because the desk will NOT be moving. Instead, the structural integrity of the desk will fail at some point when enough force is applied in attempt to move it against the concrete floor. It's clear that the concrete floor is structurally stronger than the desk, which I assume is made of wood.

So yes, there will be some energy expended by you or something else pushing down on the desk, but you can't compute it using the standard work function formula of force X distance. You can't use formulas blindly, since the result is nonsense: zero distance moved, therefore no work is done.

To figure how much work is done by your muscule pushing down on the desk would depend on how much force you're able to apply and for how long. Since the desk did not move, the energy expended on pushing down on the desk is all converted into heat.

Answer 3

You have exerted effort (because you pushed). This made you lose some energy. But the table puhed back with the same amount of force (by action-reaction principle). Total force: 0. Total work: 0

The energy you spent was transferred not to the table as a whole, but to the surroundings (air warmed up, table surface a bit dented and bent, your straining voice, etc.) You may have done no work on the table itself, but you did work on other points around you while doing so.

The principle behind the W=Fd equation is you are in an isolated system, wherein the only things in the system are you and the table in the example. However, when pudhing on the table, you and the table are not in an isolated system, hece no wok may have been done on the table, but energy lost is dissapated.

Answer 4

Your body is a biological system and needs energy to exert a force, even when carrying a box, if the box doesn't move up or down, you are still not doing any work on it, think about work in this way, the more work you've done to the box, the more work the box can do, either by falling down, or weighing down a teeter toter to lift something else up. If you carry a box really high up, you would do a lot of work on the box, and then once you drop it down, all that work is going to turn into the velocity of it falling.

Answer 5

Nice doubt yaa...Yes, U r doing some work.The enerfy U lost will do the work of vibrating the atoms in the desk,If u give some more energy to that the vibrations will be more and the desk may break. If any material absorbs sound waves means what ,it just vibrate the atoms in that & that energy is consumed in that way.

Answer 6

No, you are not doing any work. W=F.dr. No movement, no work.
Note that this is not strictly true as you are doing some work in moving your arms.

From the first law of thermodynamics Delta U = Q + W.
Since work is zero, all the energy is being dissipated in the form of heat (after a while of pushing the desk your muscles will "warm up")

Answer 7

You are doing no work on the desk because it does not move.

You are doing work in your arm because your muscle fibers are contracting and providing a force through a (short) distance.

Answer 8

wot do you mean by "do I do any work"? in any case if the desk doesnt move you are too weak to push it hard enough or you are not exerting enough force upon it! at any rate you do expense a certain amount of anergy no matter how hard you push so yes you do some amount of work if by work you mean to say that you are using energy.

Answer 9

in theory and under the right circumstances you could very well have prevented the desk from blowing away - in which case you are to be commended for doing a marvelous job. a paperweight is not expected to push the paper through the surface upon which it rests. does it not perform an admirable function.

Answer 10

No you do not do any work. Its the same as stalling an electric motor. The motor will get hot but no work is being done.

The energy that you are using is making your muscles hot and performing a chemical reaction, but no work in the physics sense.

Answer 11

No, if the desk is not moving, no work is done. If you lifted weight for an hour, but the weights started and ended up in the same place, then you may be exhausted but no work is done.