Ramp collision lab

1. Pick what to test. Under Your experiment, pick ONE thing to change: Car 2 mass, Car 1 mass, the release point or the ramp height. That is your manipulated variable. The class lab tests Car 2 mass.
2. Keep everything else the same. The controlled variables are listed under it. A ✓ means it matches your earlier trials. A ⚠ means it changed, so the test is not fair anymore.
3. Load the cars. Tap a hooked mass to drop it in a car's tray. Car 1 (red) is the source car. It rolls down the ramp. Car 2 (blue) is the receiver car. It waits at the bottom. Each car is 60 g before you add mass.
4. Set the ramp. Ramp height moves the clamp up or down the ring stand. Release point is where Car 1's front bumper starts, measured along the ramp from the bottom. The green marker on the ramp shows it.
5. Press Release Car 1. Car 1 rolls down, hits Car 2 and the two cars hook together. Read the distance at Car 2's back bumper. It starts on 0 cm, so its reading is how far it moved.
6. Do 3 trials for each value. Press Release Car 1 three times, or press Run 3 trials. The data table puts each value's trials in one row. Find the average yourself: add the 3 trials, then divide by 3. The graph shows each average as a big dot, so you can check your graph.
7. Went too far? The two meter sticks reach 200 cm. If Car 2 rolls past the end, the trial can't be measured and is not saved. Lower the release point or the ramp, then keep that setting for every trial.
8. Save your work. Copy data copies the table so you can paste it into a spreadsheet. Delete last trial takes back one trial. Clear trials starts this test over (click it twice).

Car 1 rolls down the ramp and speeds up. It hits Car 2, and the two cars hook together. Then they move as one and slide until they stop.

A moving car has momentum. Momentum is how hard something is to stop. More mass or more speed means more momentum. When the cars hook together, Car 1's momentum is shared by both cars.

What each change does

• More mass on Car 2: the same momentum is shared by more mass. The pair moves slower, so Car 2 goes a shorter distance.
• More mass on Car 1: Car 1 brings more momentum. The pair moves faster, so Car 2 goes farther.
• Higher release point or taller ramp: Car 1 starts higher, so it is going faster at the bottom. The pair moves faster, so Car 2 goes farther.

Rolling resistance is a small force from the wheels and the bench. It slows the cars down by the same amount every second. That is why a faster pair always slides farther before it stops.

Look at your graph. Is it a straight line or a curve? When the pair goes twice as fast, it slides about four times as far. That is why some graphs curve.

Words to know

Manipulated variable

The one thing you change on purpose. Here it is the button you picked under Your experiment.

Responding variable

What you measure to see what happened. Here it is the distance Car 2 travels.

Controlled variables

Everything you keep the same, so only the manipulated variable can change the result.

Source and receiver

The source object gives the push (Car 1). The receiver object gets the push (Car 2).

Momentum

How hard a moving object is to stop. It is mass times speed.

Rolling resistance

A small force from the wheels and the bench that slows the cars down.

What each letter means

Letter	What it stands for	Unit
m1	Mass of Car 1, the source car (60 g plus any added mass)	g
m2	Mass of Car 2, the receiver car (60 g plus any added mass)	g
h	Height of the release point above the bench	cm
g	Gravity's pull: always 980	cm/s²
v1	Speed of Car 1 at the bottom of the ramp	cm/s
v	Speed of both cars together, right after the hit	cm/s
a	How fast rolling resistance slows the cars: always 58.8	cm/s²
d	Distance Car 2 travels (at its back bumper)	cm

Three steps

1. Car 1's speed at the bottom. A higher release point gives more speed. The 0.96 is there because the ramp takes away a little energy.
   v₁ = √(2 × g × h × 0.96)
2. Speed after the hit. The momentum before the hit equals the momentum after. Car 1's momentum is shared by both cars.
   v = (m₁ × v₁) ÷ (m₁ + m₂)
3. How far Car 2 slides. The speed is squared, so twice the speed gives four times the distance.
   d = v² ÷ (2 × a)

 

Your measured distances are a little different from this, because of the real-lab wobble. Turn the wobble off and they will match.