A.2.21—Explosions
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- SL
Model an Explosion with Momentum Conservation
Explosion model
An explosion is an interaction in which an initially combined system separates into parts. If the external impulse is negligible, total momentum before and after is equal.
Use a sign convention
For an object initially at rest, the vector momenta after the explosion sum to zero. In one dimension, equal and opposite momenta can give different speeds when the masses differ.
Energy is separate
The chemical, elastic or other internal energy released can increase total kinetic energy while momentum remains conserved.
Common trap
Do not assume the fragments have equal speeds. Momentum magnitudes are equal and opposite only when the initial total momentum is zero.