Forces (Newton’s second law) Simulation — Description
What the simulation is
This is an interactive 3D model of the AQA GCSE required practical on force and acceleration (Newton’s second law, RPA7). A trolley sits on a level aluminium runway. A string runs from the trolley, over a pulley at the end of the bench, down to a hanger carrying slotted masses. The falling masses provide the pulling force. Two light gates straddle the track, and a card fixed on the trolley breaks each beam so the data logger works out the speed at each gate, then the acceleration from the change in speed over the time between them.
Pupils build the apparatus through guided steps by tapping and dragging: they level the track with a shim to compensate for friction, set the two light gates 60 cm apart, fix the card on the trolley, set the force or mass, then release the trolley and watch it accelerate through both gates. Each release records one reading, and the results plot onto a graph board.
There are two investigations, switchable in the header.
In “vary force”, the total system mass stays fixed at 1.000 kg. Pupils move 100 g masses one at a time from the trolley to the hanger, so the pulling force rises while the mass stays the same. The graph of acceleration against force is a straight line through the origin, showing acceleration is proportional to force.
In “vary mass”, the pulling force stays fixed at 1.96 N. Pupils stack extra masses onto the trolley, so mass rises while force stays the same. Acceleration falls, and a plot against one over mass gives a straight line, showing acceleration is inversely proportional to mass.
The whole thing carries the ClassAdapt house style and the full Adapt accessibility suite, so it works on a projector and adapts for a range of learners.
Suggested class activity: “Predict, run, explain”
This works as a paired or whole class session lasting about forty minutes, and it leans on the key idea examiners test most: why mass is moved rather than added.
Start with a prediction round. Before touching the simulation, show pupils the “vary force” setup and ask each pair to sketch on mini whiteboards what they think the acceleration against force graph will look like, and to write one sentence saying why. Collect a few predictions so the class is committed to an outcome.
Run the investigation together. Work through all six force readings on the projector, pausing at each release so a pair reads out the force and the acceleration before the next mass moves across. Build the graph live. Then compare the real line against their predictions and draw out that the line goes through the origin, which means no force gives no acceleration.
Target the moved mass idea. Ask the class the exam favourite: why do we move a mass from the trolley to the hanger instead of just hanging an extra one on? Give them a minute in pairs, then reveal the on screen readout that shows the total system mass staying at 1.000 kg throughout. The point to land is that a fair test needs the mass held constant while only the force changes.
Switch and contrast. Run two or three readings of the “vary mass” investigation and ask what is different about this graph and why acceleration now falls as mass rises. Pupils should connect both halves back to the single relationship, that force equals mass times acceleration.
Exit ticket. Each pupil writes an answer to one question: “A student adds a mass to the hanger and their force against acceleration line does not pass through the origin. Suggest one thing they may have done wrong.” Strong answers will mention friction not being compensated by the tilt, or the total mass not being kept constant.
For adaptation, offer three entry points. Some pairs just describe the shape of each graph in words. Some read values off and state the relationship. Some calculate the gradient and link it to the mass or the force. The accessibility menu lets you set text scaling, the reading ruler, and a buttons only mode for pupils who find dragging hard.