2-D Elastic Collisions
Send two disks toward each other with a chosen impact parameter — adjust their masses, starting speeds, and how off-center the hit is to see a head-on collision exchange velocities and a glancing one deflect both disks sideways, momentum and kinetic energy conserved exactly.
Preview — sign up free to change the numbers yourself
What you can adjust
- Mass 1
- 0.5 – 10 kg
- Mass 2
- 0.5 – 10 kg
- Initial velocity 1 (x)
- -10 – 10 m/s
- Initial velocity 2 (x)
- -10 – 10 m/s
- Impact parameter (b)
- -1.5 – 1.5 m
Mass of the left-hand disk (starts moving right, toward the other disk).
Mass of the right-hand disk.
Disk 1's starting horizontal velocity. Positive = moving right, toward disk 2.
Disk 2's starting horizontal velocity. Negative = moving left, toward disk 1.
The vertical offset between the two disks' starting centers. 0 = perfectly head-on; larger magnitudes make the collision more glancing, and past the disks' combined radius they miss entirely.
About this simulation
What it shows
Two disks approach each other, offset by a chosen impact parameter, and collide once. Their paths before and after the hit are drawn.
The key idea
The collision is elastic, so total momentum and total kinetic energy are both unchanged. The push acts along the line joining the centres, so an off-centre hit sends both disks off sideways.
Try this
Set Impact parameter (b) to 0 for a head-on hit, then 0.6 for a glancing one: at 0 the disks stay on one line, at 0.6 they deflect sideways.
The disks are smooth, so only the push along the line of centres acts. With the default masses they miss each other once b is about 0.95 or more.