AP Physics C: Mechanics / Unit 4: Linear Momentum
4.3 Conservation of Linear Momentum
Notes
If no net external force acts, a system's total momentum stays constant: $p_i=p_f$.
Practice
A 60 kg skater pushes a 40 kg skater; the 40 kg one moves at 3 m/s. The 60 kg skater moves at:
$40(3)=60v$.
A gun recoils when fired because:
Equal and opposite momentum.
Momentum of a system is conserved when:
Isolated system.
An isolated system's center of mass velocity:
$\vec p_{total}=M\vec v_{cm}$ is constant.
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