How Can I Calculate Energy and Power for an 800W Electric Motor?

In summary, the conversation discusses solving a problem involving an 800W electric motor raising a load and gaining 24,000 J of gravitational potential energy in 120 seconds. The equations to be used include power = energy / time, energy = power x time, and time = power / energy. The first step is to find the energy supplied to the motor, which can be calculated using the equation power = energy / time. The conversation ends with the student expressing their gratitude for the help provided.
  • #1
lovcullen
3
0
Energy Calculation ~~help

Homework Statement


Question )
An 800W electric motor is used to raise a load. In 120s, the load gains
24,000 J of gravitational potential energy from the motor
Calculate :
a) electrical energy supplied to the motor
b) energy wasted by the motor
c) output power of the motor
d) efficiency of the motor


Homework Equations


W=J/s


The Attempt at a Solution


I have no idea //

i've got a big school exam next Monday T-T
help me~
thank you
 
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  • #2


Welcome to Physics Forums.

What is the equation that relates power, energy, and time?

You'll have to show an attempt at solving the problem before getting help (sorry, but that's our policy).
 
  • #3


Redbelly98 said:
Welcome to Physics Forums.

What is the equation that relates power, energy, and time?

You'll have to show an attempt at solving the problem before getting help (sorry, but that's our policy).

Power = Energy x Time
Energy = Power / Time
Time = Power / Energy

Is this right ??
 
  • #4


Not quite, it's

Power = Energy / Time
etc.

Using that, can you find (a) the energy supplied to the 800 W motor?
 
  • #5


Redbelly98 said:
Not quite, it's

Power = Energy / Time
etc.

Using that, can you find (a) the energy supplied to the 800 W motor?

AH~~~~~
now i got it ~:D thank you
 

1. How do I calculate energy?

To calculate energy, you can use the formula E=mc², where E is energy, m is mass, and c is the speed of light. Another common way to calculate energy is to use the equation E=hf, where E is energy, h is Planck's constant, and f is frequency.

2. What units are used to measure energy?

The SI unit for energy is the joule (J). However, other common units for energy include calories (cal), kilowatt-hours (kWh), and electron volts (eV).

3. How do I convert between different units of energy?

To convert between different units of energy, you can use conversion factors. For example, to convert joules to calories, you can use the conversion factor 1 J = 0.239 cal. You can also use online unit converters or consult a conversion chart for more complex conversions.

4. What is the difference between kinetic and potential energy?

Kinetic energy is the energy an object possesses due to its motion, while potential energy is the energy an object has due to its position or state. Kinetic energy is typically associated with objects in motion, while potential energy is associated with stored energy, such as the energy in a compressed spring or the energy of an object at a height.

5. How does energy conservation apply to energy calculations?

Energy conservation states that energy cannot be created or destroyed, only transformed from one form to another. Therefore, in energy calculations, the total amount of energy in a system should remain constant. This means that the energy input should be equal to the energy output, and any losses or gains in energy should be accounted for in the calculation.

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