6 Energy, Work & Power

Different forms of energy

1. Kinetic Energy (K.E)

For any object to move, it requires energy. We call this energy Kinetic energy. Kinetic energy is the energy that is associated with motion (ie. movement).

The following are examples of objects which possess possess kinetic energy.

A car that is racing round a bend

A running hamster

2. Potential Energy

Potential energy simply refers to stored energy. In general, there are three types of potential energy we will learn in this topic!

a. Chemical Potential Energy (CPE)

This refers to energy that is stored in substance due to the positions of atoms and electrons in the substance (chemicals).

Below are some sources of CPE!

Food

Food contains CPE which can be converted to other forms of energy when digested by our body. What a pleasant way to store energy! Yum Yum.

Fossil Fuels

Sadly, we cannot eat fossil fuels, but fossil fuels like coal, oil and natural gas can be used to generate electricity to power the oven and microwave that heat up our food.

Batteries

Batteries are a must in this day and age, because even our phones need battery. CPE from battery becomes electrical energy and light energy, allowing us to take good photos of our food on clear, bright screens. #allforthegram

b. Elastic Potential Energy (EPE)

This refers to energy that is stored in a body due to elastic deformation (ie. squeezing or stretching)

Below are some sources of EPE!

A slinky is a soft spring - when it is compressed or stretched, it stores EPE!

A rope stores EPE when stretched too. As the man balances on the rope, his weight stretches the rope. The rope in turns exerts a force equal to his weight, so that he remains supported.

For fans of hunger games...

Katniss pulls on the bow. The bow stretches and gains elastic potential energy.

When released, this elastic potential energy is converted to kinetic energy that is quickly passed on to the arrow, allowing it to propel forward quickly.

May you never look at her bow in the same way!

For adrenaline junkies... you will be glad for EPE, because it allows bungee jumping to be possible.

An elastic (ie. stretchable) rope is tied to the jumper. Jumper takes a leap (in faith that the rope won't break).

As the jumper descends, the rope becomes taut before it starts to stretch. As it stretches, the rope gains more EPE. The rope exerts a force that pulls the jumper backwards, preventing the jumper for plunging into the rocks below.

c. Gravitational Potential Energy (GPE)

This refers to energy that is stored in a body due it its height above the ground.

You have definitely known GPE since you were young, but maybe you didn't even realise it!

Slides

Why is it that we can only slide down but not up a slide?

What are we doing when we climb up to take a slide?

Ans: When we climb up, we are actually gaining GPE, that will be converted into KE when we go down a slide. That explains why our speed increases as we go down a slide.

For adrenaline lovers, who love hair-raising activities...

You would know this scene very well. This represents moments before your harrowing experience.

But logically speaking, this is just helping you gain GPE. The higher you go, the greater the GPE, and the greater the KE later (ie. the faster you would go).

As you go down the roller coaster...

GPE is converted to KE (ie. GPE --> KE)

your height above the ground decreases (GPE decreases), but your speed increases (KE increases)!

Just like how the cash in your wallet decreases while your heart beat increases.

2. Potential Energy

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