Kinetic and Potential Energy

We have learnt that energy is the ability of a body to work. Energy is how things move and change. Energy is all around us but takes different forms. For example, it takes energy to wake up in the morning, to cook breakfast, and even to drive to school. Energy cannot be created. It can only be transformed from one form to another. The food that you eat gives you the energy to do work, including waking up in the morning. The toasts or pancakes at breakfast use energy from the toaster and stove to cook. The bus that drives you to school gets energy from fuel!

Energy can be broadly classified as potential or kinetic energy.

• Potential energy is the energy stored in a body by virtue of its position.
• Kinetic energy is the energy in a body due to its motion.

Potential energy

The energy possessed by an object due to its relative position is called potential energy. It is the stored energy that is ready to use. It can be classified into –

Potential energy

The energy possessed by an object due to its relative position is called potential energy. It is the stored energy that is ready to use. It can be classified into –

1) Gravitational potential energy –

An object suspended at height has gravitational potential energy. For example, a ball or a skier at a height. A raised hammer possesses gravitational potential energy that holds the ability to displace a nail (work).

The higher and bigger in mass, the greater would be their potential energy! The potential energy can be calculated by multiplying the mass, acceleration due to gravity (a constant), and the height of the object.

Suppose you and your friends start skiing from the same height, who would have the maximum potential energy at the top? The lightest or the heaviest guy?

2) Magnetic Potential Energy –

We have learnt that opposite poles of two magnets attract and their like poles repel. The closer the opposite poles of two magnets, the more is the potential energy in them.

3) Chemical potential Energy –

The energy stored in food, fuels, batteries are examples of chemical energy. When we eat food, the chemical energy in food gets transformed to give us the energy to do mechanical work.

4) Elastic Energy –

Spring has more potential energy when it is compressed or stretched. For example, when we wind a mechanical clock, we are storing potential energy in its spring. As the spring loosens, energy is released slowly that turns the hands of the clock! When an arrow is placed in a bow with the string pulled back, the arrow has potential energy and can go far and even hurt someone (work).

5) Nuclear Energy –

The amount of energy released when atoms split is huge. This process is called nuclear fission and the energy released can be tapped to generate electricity.

Kinetic energy

Kinetic energy is the energy of mass in motion.

Kinetic energy can be classified into five types –

2) Thermal Energy –

While baking a pizza or boiling water, the molecules in them move as they release heat, they are examples of thermal energy.

4) Electrical Energy –

Electricity is the flow of electrons around a circuit. So there is movement all around us as we switch on the lights and heaters, it also means that all the electrical appliances in our houses work on this kinetic energy!

5) Mechanical Energy –

Any visible moving body around you possesses mechanical energy – a moving car, a moving ball, a running girl, a boy playing the piano with his moving fingers, etc. Aside from this, wind and a flowing river also have mechanical energy that we harness to generate electricity.

Kinetic energy depends on the mass and velocity of the object. The greater the mass and velocity, the greater would be the magnitude of kinetic energy.

It can be represented as follows –

This means that if the velocity of the object doubles, it’s kinetic energy would quadruple!

Check Point

1. Indicate whether the following have potential or kinetic energy –

       a) A stationary apple on a tree.    b) Sunrays     c) A speeding car

       2. A sound is a form of kinetic energy that travels by _____ of particles around us.

       3. Splitting of some atoms releases ____ energy.

       4. A mechanical clock works with the help of _____ energy.

       5. Potential energy depends upon the mass and ____ of the object.

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