# Work, Power, Energy, Efficiency

• danielsmith123123
In summary: Ok, thank you so much.In summary, the mathematical definition of work is W = fd, where W is work, f is force, and d is displacement. When there is no motion in the direction of force, the work done will be 0. This applies to the problem of Planet X orbiting the moon, where the force and displacement are not in the same direction.
danielsmith123123
Homework Statement
Calculate the work done by planet X on its moon.
Planet X applies a force of 5.6 x 10^10 N on its moon and the moon is 4.0 x 10^8 km away from the planet and it continues to circle the planet in a circular orbit of circumference of 2.5 x 10^9 m.
Relevant Equations
Gravity
The answer in the textbook says 0J but I am not sure what the concept behind it is. Does it have something to do with gravity?

"Gravity" is not an equation. What is the mathematical definition (equation) of work?

russ_watters said:
"Gravity" is not an equation. What is the mathematical definition (equation) of work?
W = fd

danielsmith123123 said:
W = fd
Great, so can you apply it to this problem?

russ_watters said:
Great, so can you apply it to this problem?
W = Fd -------------- W = (5.6 x 10^10 N) (d) Would "d" be 0 because Planet X keeps orbiting the moon and essentially coming back to where it initially started therefore making it's displacement 0?

danielsmith123123 said:
W = Fd -------------- W = (5.6 x 10^10 N) (d) Would "d" be 0 because Planet X keeps orbiting the moon and essentially coming back to where it initially started therefore making it's displacement 0?
Yep, that's one way to look at it - the other is along the direction of motion there is no force. Essentially, the force and displacement have to be in the same direction. Since you don't have that, they'll multiply to zero.

russ_watters said:
Yep, that's one way to look at it - the other is along the direction of motion there is no force. Essentially, the force and displacement have to be in the same direction. Since you don't have that, they'll multiply to zero.
Ok, thank you so much

russ_watters

## 1. What is the difference between work and power?

Work is the amount of energy transferred when a force is applied over a distance. Power, on the other hand, is the rate at which work is done, or the amount of work done per unit of time.

## 2. How is energy related to work and power?

Energy is the ability to do work or produce change. Work and power are both measures of energy, with work being the total amount of energy transferred and power being the rate at which energy is transferred.

## 3. What is efficiency and how is it calculated?

Efficiency is a measure of how well a system or process converts input energy into useful output energy. It is calculated by dividing the useful output energy by the total input energy and multiplying by 100%.

## 4. How can efficiency be improved?

Efficiency can be improved by reducing the amount of wasted energy in a system, such as through insulation or using more efficient equipment. It can also be improved by optimizing the design and operation of a system.

## 5. What are some real-world applications of work, power, energy, and efficiency?

Work, power, energy, and efficiency have many real-world applications, such as in the design and operation of machines and engines, renewable energy systems, and energy-efficient buildings. They are also important in understanding and improving the efficiency of everyday tasks, such as cooking, transportation, and household chores.

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