Choose an example at the top: 🛒 Smart Cart bouncing off a force sensor · 🥚 egg thrown into a sheet, a cushion or a wall ·
🎾 ball hit by a racket, a wall or a golf club.
Set the values with the sliders, or type a value in the box next to a slider and press Enter.
A value outside the allowed range is moved to the nearest limit (the box turns orange).
Choose the positive direction (→ right or ← left). Every velocity, momentum, force and impulse gets its sign from it.
Press ▶ Start. The contact plays in slow motion (the scene shows how much slower). ◂ / ▸ (or the ← → keys)
step through the contact and pause it.
The middle column shows the free-body diagram (forces to scale) and the momentum before and after. The orange arrow
Δp = pafter − pbefore is the impulse.
Graphs: on F–t, the Area tool gives the impulse J. On p–t, the Tangent
gives the gradient Δp/Δt = the force. Zoom on the contact shows only the collision (time in ms when it is short).
● Record saves a trial. The Data tab plots your trials and draws a best-fit line; its gradient is written next to it.
Work through the Tasks tab. Write explanations on your worksheet.
The physics
p = mv (kg m s⁻¹) · a vector: choose a positive direction
J = FΔt = Δp = mv − mu (N s = kg m s⁻¹)
Impulse = area under the force–time graph (any shape). Average force F = Δp/Δt.
Same Δp over a longer time ⇒ a smaller force: airbags, crumple zones, crash mats, bending your knees, the bedsheet.
A ball that bounces back has a larger Δp than one that stops: Δp = m(v − u) with u and v in opposite directions.
Model: the bumpers behave like springs that give back part of the energy (spring 80 %, magnetic 90 % of the speed; clay
almost nothing). Bumper data fitted to the class PASCO sample runs (0.500 kg cart at 0.62 m s⁻¹). Egg, ball and club: a smooth (half-sine)
or triangular force pulse lasting Δt. The egg cracks if the force goes above 25 N (a typical value). The weight is far too small
to matter during the short contact, so the motion is drawn along a horizontal line.