STUCK IN PHYSICSAll simulationsOne-dimensional collision simulation
IB Physics SL & HL · A Level Physics · AP Physics 1 · AP Physics C: Mechanics
Two blocks. One frictionless track. Change their masses, initial velocities and the coefficient of restitution—then compare momentum and kinetic energy before and after impact.
Right is positive; left is negative. A negative velocity is allowed. Changing any setting resets the trial. Restitution is an extension where it is not explicitly required by a course.
The collision
Schematic view: the camera follows the pair, spacing auto-scales and block sizes are illustrative. The physical-time window plays over 10 screen seconds; inspect the displayed time. Impact is instantaneous in this model.
Before and after
| Quantity | Before collision | After · prediction |
|---|---|---|
| Block 1 velocity | ||
| Block 2 velocity | ||
| Block 1 momentum | ||
| Block 2 momentum | ||
| Total momentum | ||
| Total kinetic energy |
The physics behind the collision
Momentum is conserved because there is no external horizontal impulse on the two-block system. For an elastic collision, total kinetic energy is also conserved. For an inelastic collision, some becomes internal energy such as deformation and thermal energy; total energy is still conserved.
Velocities are measured in the track’s reference frame. Initially, block 1 is left of block 2, with a 5 m gap between their faces. They collide only if u₁ > u₂. There is no friction, rotation, bouncing off walls or prolonged contact-force model.
Predict, then check
1. Set equal masses, e = 1 and one block initially at rest. What happens to their velocities?
2. Keep the launch conditions fixed and reduce e. What changes: total momentum, total kinetic energy, or both?
3. Set e = 0. Why do the blocks leave with the same velocity?
4. Give both blocks velocities in the same direction. Can the one behind catch the one ahead?
The observation ends after a short post-collision interval. The blocks would continue moving on the frictionless surface. “Kinetic energy lost” means energy transferred out of translational kinetic energy, not energy destroyed.
Explore momentum and kinetic energy
Investigate two blocks colliding on a frictionless horizontal surface. Change their masses and signed initial velocities, then compare momentum and total kinetic energy before and after impact. Use the time slider to inspect the collision.
Suitable for momentum and energy topics in IB Physics SL and HL, A Level Physics, AP Physics 1 and AP Physics C: Mechanics. Coefficient of restitution is an extension where it is not explicitly required by the course.