- 8808 2348
- hello.scienceofstudy@gmail.com
- Mon - Sun 9:00AM - 5:00PM
Before you read on, you might want to download this entire revision notes in PDF format to print it out for your child, or yourself to read it later.
This will be delivered to your email inbox.
Energy is everywhere around us. It lights up our homes, moves vehicles, keeps our bodies alive, and powers almost everything that keeps our world going. Although energy is so common, we rarely stop to think about what it really is or how it can change from one form to another when needed. In this article, we will explore what energy is, how it works, and why conserving it matters.
What is energy? Energy is the capacity to do work or cause change. It is a conserved quantity, so it cannot be created or destroyed. Instead, it can only be transferred between objects or converted from one form to another.
Energy is measured in the SI unit Joules (J), which is equivalent to Nm (Newton x meter). Within a system, energy is stored in various forms.
The kinetic energy (KE) storage holds energy from an object’s motion. Any moving body, be it a sprinting athlete or moving car, uses energy from this store.
The equation for quantifying kinetic energy storage is:
KE = 0.5 (mv)
where m = mass (kg), v = velocity (m/s)
For example, the KE of a 1000kg car moving at 60km/h (approximately 16.667m/s) would be 8333.5J.
0.5 (1000)(16.667) = 8,333.5J
Gravitational potential energy (GPE) storage holds energy within an object due to its vertical position above the Earth’s surface. The higher and heavier the object, the more energy it stores. This stored energy is released and converted into kinetic energy when the object falls.
The equation for quantifying gravitational potential energy storage is:
GPE = mgh
where m = mass (kg), g = gravitational field strength (N/kg), h = height (m)
On earth, g has been defined to be 9.8 N/kg.
(1)(9.8)(5) = 49J
Internal energy, also called thermal energy, is the total kinetic and potential energy of the particles in a substance. The particles are always in random motion (Brownian motion), and their energy comes from both this motion and the forces between them.
Chemical potential energy refers to energy that is stored within the chemical bonds of molecules. Upon formation or breaking of these bonds, energy is released. Chemical potential energy can be found in batteries and the food that we eat.
Elastic potential energy refers to the energy stored when an object is stretched, squished or bent. Examples include a spring, catapult or a compressed stress ball.
Nuclear energy refers to the energy stored deep within the nucleus of an atom. This energy holds the protons and neutrons together. During nuclear reactions, this energy is released.
The law of conservation of energy states that energy cannot be created nor destroyed, and can only be transferred between different stores.
There are several ways energy can be transferred:
1. Mechanically: when a force moves an object over a distance.
Example 1: When water falls from the top of a waterfall, energy from the gravitational potential energy store is mechanically transferred to the kinetic energy store.
Example 2: Swinging pendulum.
2. Electrically: when moving electrical currents flow due to a difference in voltage.
Example: When a toy car is switched on, energy from the chemical potential energy store is electrically transferred to the kinetic energy store.
3. Through heating: when thermal energy flows from a hotter to cooler area.
Example: When water in a kettle is being heated, energy flows electrically through the heating element and is transferred to the internal (thermal store) of cold water through heating.
4. Radiation: when energy moves through electromagnetic waves, such as visible light, UV and infra-red.
Example: When a flashlight is turned on, energy from the chemical potential energy store of the battery is transferred to the internal store of the bulb filament. This energy is released through radiation as light.
In all energy transfers, the total amount of energy within the system stays constant, due to the law of energy conservation.
In physics, work is the energy transferred when a force causes an object to move in the direction of the force applied. It is calculated using the formula:
W = F x d
where W = work done (J), F = force (N) and d = distance moved by the object in the same direction as force applied (m).
In an ideal situation, energy would be transferred completely from its store into the movement of an object. In the real world, however, some energy is always lost to factors such as friction, which reduces the efficiency of the transfer.
Hence, it is important to take note of any factors that might be made known to you in the exam question.
Remember that:
Applied force = Resultant force – frictional force
The applied force is the force used to move the object, the resultant force is the net force acting on the object, and the frictional force opposes motion and slows the object down.
Power refers to the rate at which work is done, or energy is being transferred. It is measured with the SI unit Watt (W), and can be calculated with the equation:
P = E/t
Where P is power (W), E refers to energy or work done (J), and t refers to time (s).
A more powerful charger transfers energy to your phone’s battery more quickly, so the phone charges faster. That is why higher power means a greater rate of energy transfer.
Efficiency is the proportion of the input energy that is converted into useful output, usually written as a percentage. It is commonly expressed as:
Efficiency (%) = (useful energy transferred)/(total energy supplied) x 100%
Some energy is lost to the surroundings, often as heat due to friction from air, water, or the ground, so not all input energy does useful work. Hence, efficiency cannot be greater than 100%.
Energy resources are systems and materials that are used to generate electricity and power. They are divided into two primary categories, renewable and non-renewable. Renewable resources such as wind, hydropower and solar power, will naturally replenish, while non-renewable resources like fossil fuels, coal, oil and nuclear fuel are finite and do not replenish quickly after being used.
Since the invention of the steam engine during the Industrial Revolution, we have relied heavily on non-renewable energy sources to generate electricity. However, these resources are limited and cannot be replaced quickly enough to meet the world’s ever-growing energy demand.
In modern times, we have developed ways to harness energy from renewable sources such as hydroelectric power from dams, wind energy from turbines, and solar power from solar panels. Although these technologies are more environmentally friendly, they are often more expensive to set up than traditional power plants that use non-renewable fuels. This is one of the main reasons why many countries still depend on non-renewable energy sources.
When considering the pros and cons of both types of energy resources, countries must decide which option can meet energy demands while remaining affordable. However, with non-renewable resources expected to become critically scarce within the next 50 years, many nations are introducing policies to encourage a shift towards renewable energy. In the long term, renewable energy could provide a clean and sustainable source of power for future generations.
Find out more by joining us at Science of Studying!
Prepared by: Michelle
You might want to download a pdf copy of this article for future reference!
Click the white download button below, enter your email, and the pdf file will be delivered to your inbox! (Remember to check spam!)
The Science of Studying provides live online tuition via Zoom classes for Combined/Pure Chemistry, Biology, and Physics. To date, we have taught 800+ students over 12 years.
In case you are wondering, yes – there is a science behind studying!
At Science of Studying, we use our SOS system™ to teach our classes so that even last-minute students can see remarkable improvements in their grades – without mind-numbing memorisation of textbooks and without the drudgery of doing numerous assessment books.
All these conducted in a fun, interactive, stress-free online environment.
If you need help with your Chemistry, Biology, and Physics subjects, do reach out to us and we will see what we can do to help.
Contact Us: Click Here
Admin number: +65 88082348
The SOS system™️ guides students through an effective process of:
Join our proven online tuition programs and see real improvements in understanding, confidence, and school results.
Book a free trial lesson and start the journey today or discover more below:
