Energy Power and Work

ENERGY, POWER AND WORK

We use energy in our daily activities. Both work and energy are common words in our normal everyday language. When we have toiled all day on the farm and we are tired, we often say that we have no energy left and cannot work anymore. When we take a good meal and have some rest, we feel strong again and can continue our work. It is clear from this that energy must be stored up in our muscular system so that it is made available if we are to do work. The energy is used up when work is done. The stored up energy (potential energy) is converted to kinetic energy as work is being done. Since work done is a measure of energy, both work and energy are measured in the same units, joules (J).

We shall determine the quantity of work done and calculate the potential and kinetic energy of a given body that does work. We shall also discuss some means of doing work and calculate the mechanical advantage and efficiency involved when work is done with the help of a machine.

CONCEPT OF WORK
You are already familiar with different sources of energy and know that a moving body possesses energy. Here is a simple activity which will help you see that energy is necessary for doing work.

CONCEPT OF ENERGY
Energy is defined as the ability to do work. Energy can exist in different forms. These forms of energy are mechanical, chemical, electrical, heat, light, sound and atomic energies.
Mechanical energy consist of potential energy and kinetic energy.

CONCEPT OF POWER
The rate at which work is done is very important to a farmer, a factory owner and various aspects of human activities. The time it takes a child to walk to school or to a farm with a load cannot be compared with the time one taxes using a motorcycle to do a similar work. The rate for each work done above will certainly be different.
The work done per unit time by any device or machine is known as power “P”. Power is defined as the rate of doing work.

SIMPLE MACHINES

When we think of machines we probably have a picture of complicated pieces of mechanism like a motor car engine, a printing press, or a turbine. These indeed are machines. They are all, however, based on very much simpler arrangements. They look complicated because they are big and have lots of parts, but in fact all the parts are really simple machines which depend on one another to work properly.

A machine is any arrangement that enables us to do work more easily. It may be, that we otherwise would not be able to do this work because we are not strong enough or because we are prevented for some other reason from doing it directly.

For example, if my car gets a puncture, I have to change the wheel. To do this, I have to lift the car; but it is too heavy for me – I have not the strength to do it. So I use a machine (a car jack) to lift the car. Then when the car is lifted, I have to get the wheel off. To do this, I have to unscrew some nuts. They are screwed on very tightly (otherwise the wheel would come off when the car is moving) and I cannot move them with my fingers because they are not strong enough. So I use another machine (a spanner) to undo the nuts. Then I have to get the tyre off the wheel. This is not easy, so I use another machine to help me get the tyre off – a tyre lever. Then, when I have repaired the puncture, I have to blow up the tyre. I do not have the strength to blow it up with my own lungs so I have to use another machine – a pump.

Any device that makes it easier for us to do work is a machine. The purpose of using a machine is to do work more conveniently. In our homes there are many machines. It is likely that you do not think of calling some of them machines. You may have, for example, brooms, knives, hoes, and axes. Apart from these simple machines, you may also have more complex ones like a sewing machine, a pump, a bicycle, and a car jack. Can you name any more examples of complex machines?

Two of the basic machines from which all the others are made up are the lever and the inclined plane. We will discuss the lever, the inclined plane, the screw, and the wedge as examples of simple machines.
We will also mention the pulley and the ‘wheel and axle’. Then we will compare machines with body movements and discuss the maintenance of machines.

LEVERS

Put your phone on the table, and slip a ruler underneath it.
Let the ruler stick out over the edge of the table. Press on the ruler and you will be able to lift the phone. The ruler is being used as a lever.

In order to use the ruler to lift the phone in this way, you had to pivot it at the edge of the table and press down on one end of the ruler. In other words, you had to apply a force. The other end of the ruler lifted the phone and so it applied a force to the phone. What the lever did was to transfer the force applied one end to the other.

There are some terms that are used about levers that we must learn. The force applied is called the effort; the object being lifted is called the load; and the point of pivoting is called the fulcrum.

About The Author

Leave a Reply

Your email address will not be published. Required fields are marked *