Energy Forms & Conservation Cheat Sheet

A printable reference covering kinetic, potential, thermal, chemical, electrical, radiant, sound, nuclear energy, and conservation of energy for grades 6-8.

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This cheat sheet covers the main forms of energy students meet in middle school physics and explains how energy changes from one form to another. Students need it because energy appears in motion, heat, electricity, light, sound, food, fuels, and machines. A clear reference helps connect everyday examples to physics ideas and formulas. The most important idea is that energy is conserved, which means the total amount of energy stays the same in a closed system. Energy can be stored as potential energy, carried by motion as kinetic energy, or transferred by work, heat, light, sound, and electric currents. Useful formulas include $KE=\frac{1}{2}mv^2$ , $GPE=mgh$ , $W=Fd$ , and $P=\frac{E}{t}$ .

Key Facts

Kinetic energy is the energy of motion and is calculated with $KE=\frac{1}{2}mv^2$ , where $m$ is mass and $v$ is speed.
Gravitational potential energy is stored energy due to height and is calculated with $GPE=mgh$ , where $g\approx 9.8\,\text{m/s}^2$ on Earth.
Elastic potential energy is stored in stretched or compressed objects and can be modeled by $E_e=\frac{1}{2}kx^2$ for springs.
Energy conservation means $E_{\text{total before}}=E_{\text{total after}}$ when no energy enters or leaves the system.
Work transfers energy when a force moves an object through a distance, and the formula is $W=Fd$ when force and motion are in the same direction.
Power measures how quickly energy is transferred, and the formula is $P=\frac{E}{t}$ or $P=\frac{W}{t}$ .
Mechanical energy is the sum of kinetic and potential energy, so $ME=KE+PE$ .
Thermal energy usually increases when friction acts because some mechanical energy is transformed into heat.

Vocabulary

Energy: Energy is the ability to cause change or do work and is measured in joules, written as $J$ .
Kinetic Energy: Kinetic energy is the energy an object has because it is moving, calculated by $KE=\frac{1}{2}mv^2$ .
Potential Energy: Potential energy is stored energy due to position, shape, or condition, such as $GPE=mgh$ for height.
Conservation of Energy: Conservation of energy means energy cannot be created or destroyed, only transferred or transformed.
Work: Work is an energy transfer that happens when a force moves an object through a distance, calculated by $W=Fd$ .
Power: Power is the rate of energy transfer or work done, calculated by $P=\frac{E}{t}$ .

Common Mistakes to Avoid

Confusing energy with force, because force is a push or pull measured in newtons $N$ , while energy is the ability to do work measured in joules $J$ .
Forgetting that speed is squared in $KE=\frac{1}{2}mv^2$ , because doubling speed makes kinetic energy four times larger, not two times larger.
Treating lost mechanical energy as destroyed, because friction transforms some mechanical energy into thermal energy instead of making it disappear.
Using height without a reference level in $GPE=mgh$ , because gravitational potential energy depends on the chosen zero height.
Mixing up energy and power, because energy is an amount such as $E=100\,J$ , while power is a rate such as $P=100\,W$ .

Practice Questions

1 A $4\,\text{kg}$ cart moves at $3\,\text{m/s}$ . Find its kinetic energy using $KE=\frac{1}{2}mv^2$ .
2 A $2\,\text{kg}$ book is lifted to a shelf $1.5\,\text{m}$ high. Find its gravitational potential energy using $GPE=mgh$ with $g=9.8\,\text{m/s}^2$ .
3 A student does $300\,J$ of work in $6\,s$ . Find the power using $P=\frac{W}{t}$ .
4 A ball rolls down a ramp and speeds up. Explain how its gravitational potential energy, kinetic energy, and thermal energy change if friction is present.