Describing Inertia

Part A · Rear-end tap

1. The bottom chip is already stuck to the double‑sided tape on the front deck of the car. Without disturbing it, a second chip is resting on top with the grooves lined up.
2. Predict: when the loaded car is tapped from behind, what will the loose chip do? Pick your prediction in the panel before you run it.
3. Choose Rear‑end tap, set your force, and tap the car. Record what actually happened in your data table.
4. Run it again at a gentle force and again at a hard force. Look for the point where the result changes.

Part B · Front-end tap

1. Reset to reload the chip on the car.
2. Predict: when the loaded car is tapped on the front end — the same thing that happens when a rolling car runs into your hand — what will the loose chip do?
3. Choose Front‑end tap, run it, and record the result.

Follow up · answer in a complete sentence

• Which object did you apply a force to — the car, the chip, or both?
• How could that force explain the difference between the car’s motion and the chip’s motion?
• Claim: The poker chip will move ________ your hand when a force is applied to the car. (Use your data from both tests to fill in the blank.)

Inertia is an object’s resistance to a change in its motion. An object at rest stays at rest, and an object that is moving keeps moving the same way, until an unbalanced force acts on it. That sentence is Newton’s First Law of Motion.

Here is the key move in this lab: you never touch the loose chip. Your hand pushes on the car. The car changes its motion right away because the force is applied directly to it. The chip only feels one sideways force — friction from the chip taped underneath it. Friction is a weak grip, so when the car changes speed too quickly, friction is not strong enough to drag the chip along with it. The chip keeps doing what it was already doing, and the car slides out from under it.

Why the force setting changes the answer

A gentle tap changes the car’s speed slowly. Friction between the two chips is strong enough to keep up, so the chip rides along and nothing seems to happen. A hard tap changes the car’s speed very quickly. Friction cannot keep up, the chip slips, and it slides right off. Same setup, different force — and that is what makes this a fair test.

In this model there are three things that can happen, and you can find all three with the slider:

• Below about 2.4 m/s² friction never loses its grip. The chip and the car move as one object.
• Above that, the chip slips. If the car slows down again quickly enough, the chip catches up and friction grabs it before it reaches the edge — so it stays on, just out of place.
• Slip past about 2.1 cm and the chip runs out of chip to sit on. It tips off and lands on the bench, and the car keeps rolling without it.

Both tests, one answer

• Rear-end tap: your hand is behind the car. The car jumps forward, the chip stays put, so the chip ends up behind the car — on your hand’s side.
• Front-end tap: your hand is in front of the car. The car is pushed backward, the chip stays put, so the chip ends up in front of the car — again on your hand’s side.
• The chip never really “flies” anywhere. It mostly stays where it was while the car moves away from it. That is inertia you can see.

1. Pick Rear‑end tap or Front‑end tap. This chooses which side your hand taps.
2. Drag the force slider from 1 to 10 to set how hard you tap. The words under the slider tell you how hard that is.
3. Choose a prediction if your teacher asks you to. The simulation will tell you afterward whether you were right.
4. Set the playback speed. The real event takes less than a tenth of a second, so start on Slow or Super slow so you can actually see the chip slip.
5. Press Tap the car. Watch the arrows: the blue arrow is the car’s speed, the red arrow is the chip’s speed.
6. Read the four numbers under the bench. Chip slip on car tells you how far the loose chip has slid across the taped chip — once it passes about 2.1 cm, it tips off.
7. Press Reload the chip & reset to set the car back up, then change one thing and try again. Every run is saved in the trial log below.