Mechanics · Momentum
Chapter 1 · 3
The idea
Conservation of linear momentum
The principle that the total momentum of a system is unchanged by a direct collision — how to set it up with a consistent positive direction, the special case where the bodies coalesce (stick together) and move with a common velocity, and how to read the sign of the answer as a direction.
A full journey — read it, play with it, work it, then earn real exam marks. Everything stays on the timeline below.
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Mechanics · Momentum
Conservation of linear momentum
The principle that the total momentum of a system is unchanged by a direct collision — how to set it up with a consistent positive direction, the special case where the bodies coalesce (stick together) and move with a common velocity, and how to read the sign of the answer as a direction.
Why it works
Equal, opposite, and for the same time
When two bodies collide directly (moving along the same straight line, hitting head-on or one catching the other), the forces they exert on each other are equal and opposite, and they act for the same length of time. The effect on the total momentum of the two bodies cancels out. So, provided no other external force acts along the line during the impact,Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
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