5th Class Science Work, Force and Energy Energy


Category : 5th Class

*     Energy


We require energy to do work. We get lots of nutrients from plants and animals, which are the source of energy. These nutrients in our body is digested and give us energy. A small animal like ass cannot carry load equal to the load carried by an elephant. Hence, the energy is the capacity to do work. Every movement in our universe is carried out by the consumption of energy.

Therefore, we need different forms of energy to do various types of work. Heat energy is required to boil the water. Our voice and sound produced by the different objects possess sound energy. Mechanical energy is required to lift and or move an object. We use muscular energy to move our body. A bulb in our house works on electrical energy. Mechanical energy is further divided into two groups, kinetic and potential energy.


*        Kinetic Energy

The energy that an object possesses by its motion is called kinetic energy. A stone thrown on the glass, breaks the glass due to kinetic energy. A ball hits the stamps due to the kinetic energy. Therefore, a moving object possesses kinetic energy. Kinetic energy of a moving object is depends on the mass of the object. If the mass of the object is more, it possesses greater kinetic energy.

If we throw an iron ball slowly on a soft piece of land, the ball will float on the surface. If thrown fast then the ball will dig the land and will enter into the lower surface. Hence, the kinetic energy of an object is dependent on the speed of the object.

Look at the following picture of examples of kinetic energy:


A running car possesses kinetic energy 


A running boy possesses kinetic energy  


*         Potential Energy

When a body is placed at certain height from the surface of the earth, the energy it possesses is called potential energy. The formula to calculate the potential energy is m x g x h. Where, m = mass of the body, g = gravitational pull by the earth and h = height of the body from the surface of the earth.

Therefore, the potential energy of a body depends on the mass and height at which the body is placed from the surface of the earth. The potential energy will increase on increasing the height from the surface of the earth and also the mass of the body.


Look at the following picture, the example of potential energy::


In the above picture a ball of mass m is placed at the height of h. The ball possesses potential energy and energy possesses by the ball is calculated by the formula: product of mass of the ball, gravitational pull or gravitational constant (9.8) and height from the surface of the earth. Hence the potential energy possessed by the ball = m x g x h.


*         Principle of Conservation of Energy

The energy possesses by a body is always remains constant and no energy is externally supplied and taken away from the body. But the energy stored in the body is transformed from one form of energy to another form. This principle of energy is known as the conservation of energy.


*         Sources of Energy

Sun is the primary source of energy for all living organism. Plants require sun energy for making food for themselves, which gives the energy to the plant for their internal activity. We know that all living organism directly or indirectly depend on the plants, hence the plants are the source of energy for rest of the living organism.

Wind and water are also the source of energy, which are used for the generation of electricity.

Depending upon the availability of different sources of energy, it can be classified into two types, renewable and non renewable source of energy.


*         Renewable Sources of Energy

The sources of energy which are constantly replenished by nature are called renewable sources of energy. For example. Sun, Wind and Water.


*          Non - Renewable Sources of Energy

Some sources of energy require millions of years to be formed. These sources of energy are called non - renewable sources of energy. For example, fossil fuel..

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