Momentum and collisions
Before you start
A moving cart can set another cart in motion. Their momentum changes together, even when their masses differ.
The setupA starts on the left and B on the right of a frictionless track. Rightward velocities are positive. Contact bumpers compress like springs; elastic mode releases that energy, while sticking mode traps the compression and transfers the stored energy internally.
What to do and noticePlay through the slowed contact. Orange force arrows have equal lengths and opposite directions because FA = −FB. These forces act for the same time, so ΔpA = −ΔpB and total p = mAvA + mBvB stays constant. Acceleration F/m can still differ.
Predict firstWhich cart moves after an elastic collision with a stationary equal-mass cart?
Use the same before-and-after readings to test two different conservation statements.
Prerequisites: Momentum p = mv has direction; kinetic energy mv²/2 is a scalar. Always identify the system.Start with equal masses
Predict firstWhich cart moves after an elastic collision with a stationary equal-mass cart?
In one dimension, equal masses exchange velocities in an elastic collision. Play and follow the blue energy marker from A to B. The carts exchange momentum through interaction; their masses are not transferred.
How to observe
- Pause before and after contact to compare momentum
- Test velocity exchange in an equal-mass elastic collision
- Switch to a sticking collision and follow internal energy
Model notes
One-dimensional collisions with no external horizontal impulse. A 100000 N/m contact spring compresses and releases; contact is slowed for teaching. In sticking mode a latch captures peak compression and converts stored contact energy into internal energy. Wheel rotation is omitted.