How much power is needed to hold a 500g object stationary against gravity?

[priesty100]

Hi, I am trying to calculate the electrical power (watts) needed to hold a 500g object stationary against gravity.

It’s been a while since my physics days and each time I do the calculations I come up with a different answer.

Any help would be much appreciated.

Thank you.

Sam

 

[Doc Al]

Why would it require power? Just rest it on the floor.

 

[priesty100]

A fair question,

However the object is to be suspended.

Sam

 

[Doc Al]

However the object is to be suspended.

So?..

 

[leright]

So?..

put it on a table? lol

 

[russ_watters]

A fair question,

However the object is to be suspended.

A cable attached to the ceiling will suffice.

Perhaps this is a trick question?

 

[priesty100]

Not a trick question,

Imagine the object had to be moved up and down (attached to the cable if you like). and this movement was controlled by an electric motor. To hold the object in a stationary position the motor would still have to work to overcome the effects of gravity.

 

[Doc Al]

No work is done against gravity on a stationary object. But it may well be true that your particular support device may require power to maintain a tension equal to the object's weight. But that's a question about how your motor works, not about work done against gravity. The point here is that you don't need a power source to support an object passively.

 

[brewnog]

Priesty, have a look how a crane operated. Energy is used in a motor to pull the cable and move the load. When the load is at rest, the cable is being held by a brake, not by the motor. Think of putting a brick on the brake pedal of a car on a slope; no energy is used here.

 

[Dale]

P = W/t

W = 0 -> P = 0/t = 0