In a collision, one object hands energy to another.
collision When two things crash into each other.
Step 1: Something to Notice
Watch first. The explanation comes later.
A light cart moving fast and a heavy cart moving slowly hit the same block. The light one shoves it further.
Which matters more in a crash — how heavy, or how fast?
Step 2: Find Out
Compare mass 1 at speed 4 with mass 3 at speed 2.
Step 1 — Predict
Mass 1 at speed 4, against mass 3 at speed 2. Which carries more energy?
Choose what you think will happen. You cannot see the experiment until you do — guessing first is what makes it worth watching.
Step 3: So Here Is Why
Now the explanation, after you have seen it happen.
How much depends on both
The energy is the mass multiplied by the speed, multiplied by the speed again.
Speed usually wins
Mass 1 at speed 4 gives 16. Mass 3 at speed 2 gives 12. Three times the mass loses to twice the speed.
You can send the energy elsewhere
Padding works by taking longer. The same energy has to be got rid of either way, but something soft squashes and spreads the stop over more time, so the force at any instant is much smaller. That is what a helmet, a crash mat and a car bumper all do.
A collision transfers energy
A fast marble hitting a stationary one passes energy across, and the second one moves off. The first slows down by exactly as much as the second speeds up, allowing for what turns into sound and heat.
Why crumple zones exist
Spreading a collision over a longer time and distance reduces the force on the people inside. The energy still has to go somewhere; the design decides where and how quickly.
Step 4: A Common Mistake
Lots of people think
“A heavier object always hits harder than a lighter one.”
Step 5: Why Crumple Zones Exist
The same idea somewhere new.
The energy in a crash has to go somewhere. Cars are built with parts designed to fold up and absorb it, so that it goes into bending metal rather than into the people. The energy is not reduced — it is sent somewhere harmless.
Step 6: Think It Through
Practice makes it stick.
Two Carts
Problem 1 of 2
Cart A is mass 2 at speed 3. How much energy does it carry?
units
The Padded Wall
Problem 2 of 2
A cart hits a padded wall instead of a bare one. What does the padding change?
Collisions
1 of 4
Mass 1 at speed 4, or mass 3 at speed 2. Which hits harder?
2 of 4
How do you work out the energy of a moving cart?
3 of 4
Mass 3 at speed 4. How much energy?
units
4 of 4
Does padding reduce the energy in a crash?
Step 7: Quick Check
Show what you know.
Question 1 of 1
A light cart going fast beats a heavy cart going slowly. Why?
Step 8: Explain It in Writing
Claim, evidence, then reasoning.
The question
Before each run you worked out mass × speed × speed. Using your three runs, write an argument answering the question: can you tell which cart will shove the block further before you watch it happen?
Evidence you can use
- Mass 3 at speed 2 works out at 12, and the block was pushed 13 cm.
- Mass 1 at speed 4 works out at 16, and the block was pushed 18 cm.
- Mass 3 at speed 4 works out at 48, and the block was pushed 53 cm.
- I used the same block and the same ground for all three runs.
- I expected the heavy slow cart to win, and it did not.
- The heavier cart is drawn taller on the screen.
- All three runs took the same time to play.
Words to usemassspeedenergyworked outpredictthe samefurther
Fill in all three boxes. The reasoning box is the one that matters most.
What You Found Out
- A collision transfers energy from one object to another.
- The energy is mass × speed × speed.
- Speed counts for more than mass, because it is multiplied in twice.
- Padding does not reduce energy — it changes where it goes.