Choose a situation at the bottom: Push / pull, Ramp, Lift or Stack.
Set each value with ▼ and ▲ (hold to go faster; the ↑ ↓ keys or the mouse wheel in the box also work, Shift = ×10), or type a value in the box. ↺ puts it back to its start value. Outside the classroom range the box turns amber ⚠: fine to explore, but the lab can't do this.
Move the pointer over any graph (or tap it): a dashed line shows the values where it cuts each curve, or the values of the nearest data point.
Change the values and watch the scale reading, the free-body diagram and the Graph tab.
Press ● Record to save a reading. The Data & analysis tab plots your readings; switch on the
best-fit line to check your own graph.
In the Lift, press ▲ Up or ▼ Down to ride, or ✂ Fall. Press ⏸ to freeze the ride and record.
Work through the Tasks tab. Write explanations on your worksheet.
The physics
A scale measures the normal force FN it exerts. It shows FN/g as "kg".
Push down / pull up with F: FN = mg + F (push) or FN = mg − F (pull)
On a slope: FN = mg cos θ (friction from the non-slip mat holds the box along the slope)
In a lift (Newton's 2nd law, Blocks 3–4): FN − mg = ma ⇒ FN = m(g + a), a positive upward
Stack: each block pushes on the one below with a force equal to the weight of everything above the contact.
The two contact forces at a surface are a Newton's 3rd-law pair.
Newton's laws
The badge above the scene says which law applies at this moment: 1st law — at rest or moving at a constant velocity, the resultant force is zero (ΣF = 0); 2nd law — accelerating, ΣF = ma. The table under the free-body diagram adds up the forces (ΣF) and compares them with m a (▾ folds it). Tick 3rd-law pairs to see every force with its partner: the same size and type, in the opposite direction, acting on the other body (the Earth, the floor, the string, the fluid…).