S7 - Q4 - Unit 2 Introduction: Energy
Kinetic Energy, Potential Energy, and Transformations
Learning Objectives
Distinguish between kinetic energy and potential energy and explain what factors affect each.
Identify common forms of energy and describe examples of energy transforming from one form to another.
State the law of conservation of energy and apply it to a real-world example.
Unit hook and vocabulary
~3 minutesUnit question: What is energy, and how does it move and change form in the world around us?
You use energy every second: your muscles use chemical energy to move, lights convert electrical energy to light, and a ball rolling downhill converts stored energy into motion. In this unit, we explore what energy is and how it follows predictable rules as it flows through systems.
energy - kinetic energy (KE) - potential energy (PE) - mechanical energy - chemical energy - thermal energy - electromagnetic energy - sound energy - energy transformation - law of conservation of energy - trophic level
Kinetic and potential energy
~7 minutesEnergy is the ability to do work or cause change.
Kinetic energy (KE) is the energy of motion. Any moving object has kinetic energy. More mass and faster speed both increase kinetic energy.
Potential energy (PE) is stored energy based on an object's position or condition:
• Gravitational potential energy depends on height above the ground. The higher an object is, the more potential energy it has.
• Elastic potential energy is stored in stretched or compressed materials (like a spring or a rubber band).
• Chemical potential energy is stored in the bonds of molecules (like in food or fuel).
Mechanical energy is the total of kinetic and potential energy in a system:
$$ME = KE + PE$$
As a ball rolls down a hill, its potential energy decreases and its kinetic energy increases, but the total mechanical energy stays the same (ignoring friction).
Check your understanding 1
~3 minutesAnswer questions Q-7P-1 and Q-7P-2 before moving on.
A 5 kg rock sits on a shelf 3 meters above the floor. A 5 kg rock sits on a shelf 1 meter above the floor. Which rock has more potential energy?
A parked car has no kinetic energy.
Energy transformations and conservation
~8 minutesEnergy transformation means energy changing from one form to another. The major forms of energy:
- Chemical energy: stored in molecular bonds (food, fuel, batteries)
• Thermal energy: the total kinetic energy of particles in a substance (heat)
• Electromagnetic (light) energy: energy carried by light waves
• Electrical energy: energy from moving electric charges
• Sound energy: energy carried by vibrations through matter
• Nuclear energy: stored in atomic nuclei
The law of conservation of energy states: energy cannot be created or destroyed. It can only change form or transfer from one object to another. The total energy in a closed system always stays the same.
For example: a campfire converts chemical energy (wood) into thermal and light energy. The total energy before and after is identical; it just changed form.
Check your understanding 2
~4 minutesAnswer questions Q-7P-3 and Q-7P-4 before the exit ticket.
When you turn on a flashlight, what energy transformation occurs?
The law of conservation of energy states that energy can be created during a chemical reaction.
Exit ticket
~5 minutesComplete Q-7P-5 and Q-7P-6 to close out today's lesson.
Which of the following are examples of kinetic energy? (Select all that apply)
Select all that apply.
Mechanical energy equals kinetic energy plus ______ energy. This total stays constant in a system when no energy is lost to friction or other processes.