Force Lab: Newton's Second Law
1 · Predict
You push a box across a frictionless floor with a steady force. If you push a heavier box with that same force, does it speed up faster, slower, or at the same rate as a lighter box?
- The heavier box accelerates faster
- Both boxes accelerate at the same rate
- The heavier box accelerates slower
2 · Set Up
- Open the Force Lab preset. A single box sits at rest on a frictionless floor with one constant force pushing it forward.
- Confirm the speed probe is attached to the box, then check the box's mass and the applied force's strength in the Inspector panel.
- For each row below, set the box's mass and the force's strength in the Inspector to match, run the simulation for exactly 1 second (60 frames), and read the probe's speed.
3 · Collect Data
| Mass (kg) | Applied Force (N) | Speed at t = 1 s (m/s) | Momentum at t = 1 s (kg·m/s) |
|---|---|---|---|
| 2 | 8 | ||
| 1 | 6 | ||
| 4 | 8 |
Plot applied force (x-axis) against the speed you measured after 1 second (y-axis), one line per mass tested. What does the slope of each line represent?
4 · Analyze
- For each row, divide the applied force by the mass. How does that value compare to the speed you measured after 1 second? What quantity have you just calculated?
- Compare rows 1 and 3 (same force, different mass). How much did doubling the mass change the resulting speed after the same 1-second push?
5 · Extend
- This floor is frictionless. Predict how your speed readings would change if a small constant friction force also acted on the box. Would dividing the applied force by mass alone still predict the resulting acceleration?
- A shopping cart and a loaded delivery truck can both be pushed by an engine producing the same force. Use your data to explain why they don't speed up at the same rate.
The Physics Behind This Experiment
Newton's Second Law
The net force on an object equals its mass times its acceleration. Here a single constant force accelerates the box from rest, so the speed measured after a fixed time reveals the acceleration that force produced.
Momentum
Momentum is mass times velocity. Every trial starts from rest, so the momentum at the 1-second mark shows how much motion the same push builds up in boxes of different mass.