A.2.22—Collision energy
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- SL
Track Energy in Collisions and Explosions
Track the energy store
Total energy is conserved, but kinetic energy may be transferred to internal energy, sound, deformation or chemical energy during an interaction.
Collision comparison
Elastic collisions conserve total kinetic energy as well as momentum. Inelastic collisions conserve momentum but have a lower final total kinetic energy.
Explosion comparison
An explosion can convert internal energy into kinetic energy, so final kinetic energy can exceed the initial kinetic energy while total momentum remains conserved.
Common trap
“Kinetic energy is lost” is shorthand for transferred to other stores; it is not destroyed.
A.2.22 Exam Analysis
[ 3 ]
Show that the collision is inelastic.
Retrieve the A.2 Forces and Momentum Model
Build the force model
Choose the system, draw a labelled free-body diagram, classify the interactions and resolve components. Apply Newton’s laws with the correct boundary: contact forces, field forces, friction, tension, buoyancy and restoring forces each have their own direction and conditions.
Track momentum
Use ec p=m ec v, ec J=\Delta ec p and momentum conservation only after checking external impulse. Distinguish elastic and inelastic collisions, explosions and energy transfer.
Track circular motion
The inward resultant provides ac=v2/r=ω2r. It may come from tension, gravity, normal, friction or a field force. Angular and linear descriptions are linked by v=ωr=2πr/T.
Final checks
Ask: Which body is the system? Which forces are external? Is mass constant? Is acceleration uniform or radial? Is kinetic energy conserved, transferred or increased?