Concept Of Work, Energy And Power JSS2 Basic Science Lesson Note

 WORK, ENERGY AND POWER

Energy is used up when work is done. The energy stored up in our muscular system is made available when we are to do work. The stored energy  (potential energy) is converted to kinetic energy as work is being done.

MEANING OF WORK, ENERGY AND POWER

Work

Work is done whenever a force is applied to cause a body to move. For instance when you lift a bucket from the ground to your head and stand at a point for several hours; you have only done work by lifting the bucket of water from the ground to your head, you have done no work in carrying the bucket of water as long as you remain on the spot.

Energy

Energy is the ability to work by exerting a force to move an object through a distance. Anything capable of doing work has energy. For instance, a boy running a race of 100 meters has energy because he can move some distance. Work and energy are measured in the same unit as the JOULE.

Power

 Power is defined as the time rate of doing work. If two boys of the same weight are to climb a flight of stairs of the same height, the boy that gets to the top first is said to have the greater power. This is because he has done the work of moving his weight through that height in a shorter time.

Hence, in mathematical terms, power is expressed as power = work done or energy expended/time taken.

If the work done is in joules and the time is in seconds, then the power is watts.

1 watt=1 joule per second 

Power can also be commonly expressed in kilowatts(KW), megawatt(MW) and horsepower(h.p)

1 KW=1,000W

1MW=1,00 0,000W

1 h.p=746W

CONCEPT OF WORK, ENERGY AND POWER.

 Work is the product of force and distance moved in a given direction, and the quantity of work done is always equal to the quantity of energy put in.

In science, work is said to be done when a force can move in a measured direction, i.e. i.e. work=force(f)x distance(d) moved in the direction of the force(fxd).

Work can simply be defined as the product of distance moved and the force applied in the direction of movement.

Generally, for any work done work done, there must be energy input since energy is the capacity of any system or body to do work. Both work and energy are measured in units called joules,  named after a Scientist P.joules who carried out early studies on energy.

 Force is that which changes a body’s state of rest or uniform motion in a straight line.  It can be expressed as:

Force=Mass x acceleration

i.e F=m x a

where F =force,m =mass and a =acceleration.The unit of force is Newton (N)

If force=mass x acceleration

Work=mass x acceleration x  distance

 SUN AS THE PRIMARY SOURCE OF ENERGY

The sun is the primary source of energy available for man. It does not  deplete, and cannot be used up.

The sun transmits solar energy to the Earth in the form of light and heat and this solar energy can be transformed into other forms.

Solar energy is used by green plants to manufacture their food through the process of photosynthesis. The energy stored up in green plants is made available to man and animals when they eat plant products like yam, rice,  cassava, beans grasses,, and so on.

In addition, solar energy can be converted to other energies such as chemical and electrical energy for heating homes, boiling water, and lighting our homes and streets.

Hence, the sun is the primary source of energy for life, all other sources are secondary as they are obtained from the sun.

Examples of secondary sources are

1. Food
2. Petrol
3. Wood,
4. Water
5. Chemical,
6. Magnet and
7. Battery.

FORMS OF ENERGY

Many forms of energy can be converted from one form to the other. These are some of the forms of energy.

1. Mechanical Energy
2. Kinetic Energy
3. Potential energy
4. Chemical energy
5. Atomic energy
6. Sound energy
7. Electrical energy
8. Light energy
9. Heat energy and
10. Magnetic energy