Describing Inertia

Part A · Rear-end tap

1. The bottom chip is stuck to double‑sided tape on the flat front deck of the car, right in front of the open well. A second chip rests on top of it with the grooves lined up.
2. Predict: when the loaded car is tapped from behind, what will the loose chip do? Pick your prediction 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. Press Reset to put the chip back 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. An object that is moving keeps moving the same way. This is true until an unbalanced force acts on it. That idea is Newton’s First Law of Motion.

Here is the key idea 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 acts on it directly. The chip feels only one sideways force. That force is friction from the taped chip under it. Friction is a weak grip. When the car changes speed too fast, friction cannot drag the chip along. The chip keeps doing what it was 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 can keep up, so the chip rides along. A hard tap changes the car’s speed very fast. Friction cannot keep up, so the chip slips and falls. Same setup, different force. That is what makes this a fair test.

In this model there are three things that can happen. 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 soon enough, friction grabs the chip again before it reaches the edge. It stays on, just out of place.
• If the chip slides about 2 cm, its middle passes the edge of the taped chip and it tips off. On a rear‑end tap it drops into the car’s open well. On a front‑end tap it falls off the front and lands on the bench.

Both tests, one answer

• Rear-end tap: your hand is behind the car. The car jumps forward, but the chip stays put. The deck slides out from under it, and the chip falls back into the well — toward your hand.
• Front-end tap: your hand is in front of the car. The car is pushed backward, but the chip stays put. It falls off the front of the car — again toward your hand.
• The chip never really “flies” anywhere. Watch the dotted chip started here line. The chip barely moves away from it, while the car moves a lot. That is inertia you can see.

1. Pick Rear‑end tap or Front‑end tap. This chooses which end of the car 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 sim tells you afterward if you were right.
4. Set the playback speed. The real tap lasts less than a fifth of a second, so start on Slow or Super slow.
5. Press Tap the car, right under the bench. The view zooms so the whole run fits. The blue arrow shows the car’s speed. The red arrow shows the chip’s speed.
6. Read the numbers under the bench. Chip shift on car tells you how far the loose chip moved from its spot on the car, and where it is now.
7. Press Reset, change one thing, and try again. Every run is saved in the trial log at the bottom.