Grade 12 · Week 06 · Thursday · Day 04

Force Builder Laboratory

Learning objective: Make controlled comparisons of force, mass, motion and contact forces.

45–60 min · Offline-capable · No physical apparatus required

Reading & explanation

Predict before changing anything

The Force Builder is a digital-only model of a block on a flat support. Choose mass, opposing horizontal applied forces, two optional vertical applied forces, initial velocity and elapsed time. It calculates net forces, normal support, acceleration and idealized motion if constant forces are maintained. It does not connect to a scale or real moving object.

One variable at a time

Keep horizontal net force +8 N in two trials while changing mass from 2 kg to 4 kg. The acceleration falls from +4 m/s² to +2 m/s². To isolate an opposing force, keep mass and rightward force fixed while changing the leftward force. Explain the force sum, not just the final screen number.

Pressure is not part of the experiment

The diagram's upward normal force represents ideal flat-surface support, not a hidden hydraulic device. Changing the optional upward pull changes normal while vertical acceleration remains zero in the model. Do not attempt to simulate real lift-off by entering forces outside the provided limits. All investigation paths work with no apparatus or hazardous motion.

Distinguish effects that the model cannot predict

This model prescribes separate leftward and rightward external forces rather than calculating friction from a coefficient. The force on a real sliding surface may change direction and depends on contact. The optional 2-second displacement extrapolation is valid only while the specified forces stay constant and no event changes the motion.

Vocabulary

controlled variable
A setting held constant during a comparison.
independent variable
One deliberately changed condition.
dependent variable
The measured or calculated response to that change.
initial velocity
Velocity at the beginning of the model's chosen time interval.
model limitation
An assumption or omission limiting what can be concluded.

Worked example

Trial A: m=2 kg, ΣFx=+8 N gives ax=+4 m/s². Trial B: m=4 kg, same force gives ax=+2 m/s². The acceleration halves when mass doubles.

Show direction, units, body boundaries and your calculations.

Independent science journal

Record at least three simulated trials, including balanced while moving, positive net force and a comparison with different mass. Export the JSON data.

Browser-local journal only. Export a backup for another device.

Daily · 4 Practice Questions

Public, open-book practice with feedback and an 80% correction target. It is not a supervised final.