Work, Power And Calculations Relating To Energy, Work And Power

WHAT IS WORK?

It is very important to state that, although energy and work-done share same unit, JOULES (J), they are not the same.
  1. Energy remains invariant as the capacity to do that which is not yet done. Whereas, work is said to be done when the force applied to an object moves that object. That is W = Force x Distance
  2. For instance this video will be termed work if and only if you acquire the knowledge from this lesson and do the activity after it.
  3. Energy becomes a waste when work is not done after its use.
For example, what amount of work is done by a boy who lifts a 20kg box up a height of 6m?
The Formula is mass x gravity x  height
Answer is 20kg  x  10 m/s2  x 6m  =  1200 J

What is Power?

The formula for power is P = W/t.
The unit for power is watt (W).


For example, if the time taken to 1200Joules  work is 60seconds, what is the amount of power used?

Answer is 1200Joules ÷ 60seconds = 20W

Power can be defined as the rate at which work is done.

Calculations relating to energy, work and power

A garage hoist lifts a truck up 2 meters above the ground in 15 seconds. Find the power delivered to the truck. [Given: 1000 kg as the mass of the truck] 
Gravity ≈ 9.81 m/s^2

First we need to calculate the work done, which requires the force necessary to lift the truck against gravity:
F = m x g = 1000 x 9.81 = 9810 N.
W = F x d = 9810N x 2m 
= 19620 Nm = 19620 J.
The power is P = W/t 
= 19620J / 15s 
= 1308 J/s = 1308 W

Summary

Energy is the ability to do work.
Work is done when a force is used to move an object through a distance.
Energy is measured in joules and the instrument for measuring energy is the energy meter.
  1. Power is the rate at which work is done and it is measured in watts. The more the power, the less the time taken to complete a work.
  2. Energy supplies power with which work is done.










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