Kinetic Energy Rises with the Square of Speed

Lab Brief #2

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

Energy never disappears — it just hides somewhere else.

What you'll learn

Kinetic energy is Ek = ½mv², so doubling the speed quadruples the energy that braking has to remove. A car at 60 km/h carries four times the kinetic energy it had at 30 km/h and needs roughly four times the braking distance on the same surface. Momentum, by contrast, only doubles. That difference between a linear and a squared relationship is the whole quantitative argument behind speed limits in built-up areas.

Key words

kinetic energy
The energy an object has because of its motion, equal to ½mv² in joules.
braking distance
The distance a vehicle travels while the brakes remove its kinetic energy.

Make a hypothesis first

Before you start: which will move faster, and why?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

dynamics trolley
ramp
wooden block
carpet tile
metre rule

Get ready

⚠️ Safety first

Keep the run-out lane clear and stop the trolley before it reaches the floor edge.

Step 1 of 4 · Read

Think about what you just learned: say what "kinetic energy" and "braking distance" mean in your own words before you start.

Step 2 of 4 · Do

Roll a trolley down a ramp from three release heights and measure how far it pushes a block across carpet each time. Since the distance pushed measures the energy removed, plot it against release height and check whether doubling the speed really quadruples the distance.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

A car doubles its speed. Its kinetic energy becomes:

How sure are you?😐 maybe

Question 2 of 3

When a car doubles its speed, its momentum becomes:

How sure are you?😐 maybe

Question 3 of 3

Kinetic energy is calculated using:

How sure are you?😐 maybe

Mind = blown

⚡ Static electricity is the same physics as lightning, just smaller.

Nice work!

You got 0 of 3 right.

Next: Power Is Energy Divided by Time All lessons

🎯

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✨ More to explore

🌍 Where you see this in real life: This is why airplanes can fly and why rockets reach space.

🏆 Stretch challenge (try it this week): This week, find one thing in your house that turns one kind of energy into another.

👨‍👩‍👧 For the dinner table: “Show me something at home that uses this kind of energy.”

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