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

In summary, The conversation is discussing the calculation of electrical power needed to hold a 500g object in a stationary position against gravity. The person asking for help has been getting different answers each time they do the calculations and is looking for clarification. The other person suggests simply resting the object on the floor or a table, but the person clarifies that the object needs to be suspended from a cable attached to the ceiling. The conversation then shifts to discussing the use of an electric motor to control the movement of the object and the idea that even in a stationary position, the motor would still need to work to overcome the effects of gravity. However, it is pointed out that no work is actually done against gravity on a stationary object, and the need
  • #1
priesty100
3
0
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
 
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  • #2
Why would it require power? Just rest it on the floor.
 
  • #3
A fair question,

However the object is to be suspended.

Sam
 
  • #4
priesty100 said:
However the object is to be suspended.
So?..
 
  • #5
Doc Al said:
So?..

put it on a table? lol
 
  • #6
priesty100 said:
A fair question,

However the object is to be suspended.
A cable attached to the ceiling will suffice.

Perhaps this is a trick question?
 
  • #7
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.
 
  • #8
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.
 
  • #9
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.
 
  • #10
P = W/t

W = 0 -> P = 0/t = 0
 

1. How is electrical power calculated?

Electrical power is calculated by multiplying the voltage (V) by the current (I). This can be represented by the formula P = VI, where P is power in watts (W), V is voltage in volts (V), and I is current in amperes (A).

2. What is the unit of measurement for electrical power?

The unit of measurement for electrical power is watts (W). Other commonly used units include kilowatts (kW) and megawatts (MW).

3. How do I determine the power consumption of an electrical device?

To determine the power consumption of an electrical device, you will need to know the voltage and current ratings of the device. Multiply the voltage by the current to calculate the power consumption in watts (P = VI). You can also use a wattmeter to directly measure the power consumption.

4. Can electrical power be calculated for AC and DC circuits?

Yes, electrical power can be calculated for both AC (alternating current) and DC (direct current) circuits. However, for AC circuits, the power calculation may be more complex as it also takes into account factors such as power factor and reactive power.

5. What is the difference between real power and apparent power?

Real power is the actual power consumed by a device, while apparent power is the total power that is drawn from the source. Apparent power includes both real power and reactive power, which is the power used to create and maintain electric and magnetic fields in AC circuits. The unit of measurement for apparent power is volt-amperes (VA), while real power is measured in watts (W).

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