Conservation of energy
Energy cannot be created or destroyed — only transferred from one store to another, or usefully to wastefully. The total always stays the same.
Part of your national curriculum
- Physics: energy: Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change
Lesson overview
What you'll learn in this lesson
Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change
Key learning points
- • Energy stores and transfers
- • Conservation of energy
- • Worked example
This lesson at a glance
- 26 minutes
- 17 parts to scroll through
- 3 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 17
Visual introductionPicture this
Conservation of energy
Energy cannot be created or destroyed — only transferred from one store to another, or usefully to wastefully. The total always stays the same.
In a nutshell
Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change
Learning cycle
Part 2 of 17
Learning cycle 1 of 2
Part 1 · Energy stores and transfers
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 17
Learn
Energy stores and transfers
Energy can be stored in different ways: kinetic (moving objects), gravitational potential (raised objects), chemical (food, fuel), thermal, and elastic. A change, such as dropping a ball, transfers energy between these stores, for example from gravitational potential to kinetic.
Reset break
Part 4 of 17
Pause
That's sitting 1 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 17
Learn
Conservation of energy
The law of conservation of energy states that energy cannot be created or destroyed, only transferred, stored or dissipated in different ways. The total energy before a change always equals the total energy after it, even though some is often wasted as heat.
Quick check
Part 6 of 17
Quick check
Part 7 of 17
Quick check
A falling object's gravitational potential energy mainly transfers into which store as it falls?
Reset break
Part 8 of 17
Pause
That's sitting 2 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 17
Learning cycle 2 of 2
Part 2 · Worked example
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 17
Learn
Worked example
A ball with 20 J of gravitational potential energy is dropped. Just before hitting the ground (ignoring air resistance), all 20 J has transferred to kinetic energy. In reality, a little energy is also transferred to the surroundings as heat and sound due to air resistance, but the total is still 20 J.
Quick check
Part 11 of 17
Quick check
If a raised ball has 50 J of gravitational potential energy, what is the total energy just before landing (ignoring air resistance)?
Reset break
Part 12 of 17
Pause
That's sitting 3 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 13 of 17
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 14 of 17
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
____ can be stored in different ways: kinetic (moving objects), gravitational potential (raised objects), chemical (food, fuel), thermal, and elastic.
The total energy ____ a change always equals the total energy after it, even though some is often wasted as heat.
Challenge round
Part 15 of 17
Game · Recall cards
What does the law of conservation of energy state?
Card 1 of 4
Mastery quiz
Part 16 of 17
Marked quiz
End of lesson quiz: Conservation of energy
4 questions, marked with the reasoning shown. No timer.
1. What does the law of conservation of energy state?
2. A falling object's gravitational potential energy mainly transfers into which store as it falls?
3. If a raised ball has 50 J of gravitational potential energy, what is the total energy just before landing (ignoring air resistance)?
4. A 2 kg object moving at 3 m/s has kinetic energy of
Lesson round-up
Part 17 of 17
Lesson round-up
Ready when you are
Quiz score
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Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?
Ask LunaPart 1 of 17 · Watch & discover
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Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change