Power supplied holding a mass suspended in air

In summary, the conversation discusses the concept of power and how it relates to an object falling and being suspended. While the equation for power increasing as an object falls seems straightforward, the equation for power supplied to keep it suspended is not as clear. The conversation ends with a discussion about how our bodies get tired even when no work is being done, highlighting the difference between being tired and work being done.
  • #1
piisexactly3
36
0
A problem I thought would be very simple, but can't seem to get very far with.

Taking equations from textbook: Fv = P . Nope because velocity is 0 however power cannot be 0.
Using suvat: W = Fs , s = ut + .5gt^t , therefore P = Fgt/2 , this seems like the equation for how power would increase as an object falls but not the power supplied to keep it suspended which I imagine would be constant with time.

So there it is, leaving me very fustrated as it seems like it must be really simple.
 
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  • #2
Yes. Power=Fv and if it's velocity is changing(Accelerating at g), it's power should also change.I don't think I understood you r question clearly. We don't need power,not even energy to hold things in place. Consider a book lying at rest on a table. No work is done there.

Edit. You can still use that equation. Since no distance is traveled when it's suspended, you can just plug in 0 into s in P=Fs/t
 
  • #3
Ok but hold 50 kilos out in front of you and tell my why its tiring but no work is being done?
 
  • #4
piisexactly3 said:
Ok but hold 50 kilos out in front of you and tell my why its tiring but no work is being done?
Tiring and work done are two different things.
Our bodies are not efficient. We even get tired sitting somewhere without moving.
Muscle cells in our body need constant supply of energy to stay contracted(Which keeps things lifted up) On the other hand, the table does not deform to keep things above the ground.
 
  • #5


Your frustration is understandable as this problem can be tricky to solve. When a mass is suspended in air, there are two forces acting on it: the force of gravity pulling it down and the force of the power supply pushing it up. These two forces are equal and opposite, resulting in a state of equilibrium where the mass remains suspended. In this case, the velocity is indeed 0, but power is still being supplied to counteract the force of gravity.

The key to solving this problem is understanding that power is the rate at which work is done. In this case, the power supplied is equal to the force of the power supply multiplied by the velocity of the mass. Since the velocity is 0, the power supplied is also 0. However, this does not mean that the power supply is not doing any work. It is still exerting a force to keep the mass suspended, but since there is no movement, no work is being done.

To find the power supplied, you can use the equation P = Fv, where F is the force of the power supply and v is the velocity of the mass. Since v is 0, the power supplied will also be 0. This does not contradict the fact that the power supply is still exerting a force to keep the mass suspended. It simply means that no work is being done because there is no movement.

In summary, the power supplied to hold a mass suspended in air is 0 because there is no movement. However, the power supply is still exerting a force to maintain the state of equilibrium. It is important to distinguish between power supplied and work done in this scenario. I hope this explanation helps to clarify the problem for you.
 

1. How does the power supplied affect the mass suspended in air?

The power supplied directly affects the force applied to the mass suspended in air. The higher the power supplied, the greater the force and the higher the mass can be lifted.

2. What factors determine the amount of power required to hold a mass suspended in air?

The amount of power required depends on the weight of the mass, the strength of the force holding the mass in place, and any external factors such as air resistance.

3. Can the power supplied holding a mass suspended in air be calculated?

Yes, the power supplied can be calculated using the formula P = F x v, where P is power, F is force, and v is velocity. The force can be determined by multiplying the mass by the acceleration due to gravity (9.8 m/s^2).

4. How does the angle of suspension affect the power required to hold a mass in air?

The angle of suspension can affect the amount of power required to hold a mass in air. For example, if the mass is suspended at an angle, the force required to hold it in place will be greater than if it was suspended vertically.

5. Is there a limit to the amount of power that can be supplied to hold a mass suspended in air?

Yes, there is a limit to the amount of power that can be supplied to hold a mass suspended in air. This limit is determined by the strength of the material holding the mass in place and the force of gravity acting on the mass.

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