Force & Energy Lab

Teacher notes

The cart starts at rest on a horizontal, frictionless 40 m track. Its 1 kg base mass includes its booster; changing booster size changes force only. Thrust is constant until the cart reaches the wall. Cart acceleration is F/m during travel, and the booster shuts off at contact. The displayed collision force is an average estimate based on a fixed 1.0 m stopping distance: F = KE/d. The wall's normal force on the cart and the cart's reaction force on the wall are shown with equal magnitudes and opposite directions. The wall wobble is an energy-scaled visual cue only; Humpty Dumpty rides with the rigid wall and never falls.

The head-on collision runway models a one-dimensional, perfectly elastic collision. Students choose both objects and their opposing launch speeds. The model conserves total momentum and total kinetic energy; each object’s after-collision velocity follows the elastic-collision equations. The displayed contact force is an average estimate using a fixed 0.25 m total compression distance, not a measured peak force. During contact, the two objects exert equal-magnitude, opposite-direction forces on each other.

The tower models free fall without air resistance. Its impact-force estimate uses a fixed internal stopping rule: d = 0.30 m, a = v²/(2d), and sand contact force = ma + mg. These assumptions are not student controls or required calculations. All objects share this rule; shape, bounce, and material differences are ignored. Tower stopping acceleration is deliberately absent from student readings and graphs.

The sand meter tracks only the kinetic energy present at first contact, so its final value equals the recorded impact KE. Gravity's small extra contribution during sinking is outside this student meter. Tower falls use real elapsed time and 9.8 m/s² gravity; only the collision is slowed. Crater and debris size are qualitative indicators of impact energy/force, not a calibrated crater law. Drawings are schematic. The two required evidence sets are tower mass and cart energy. Entering Test mode clears the selected simulation’s current table rows and graph points; head-on collision remains an Explore-only source of supplemental evidence. This is an independent instructional simulation, not an official OpenSciEd product.