Recoil and conservation of momentum
An astronaut (60 kg) at rest in space throws a 2 kg tool at 6 m/s. What is her recoil speed?
Answer A: explanation for every choice
A
Correct. Total momentum stays zero: (2)(6) = (60)v, so v = 0.2 m/s.
B
This splits the tool's speed in half instead of using momentum.
C
This gives the astronaut and tool equal speeds instead of equal and opposite momenta.
D
This inverts the mass ratio.
TakeawayRecoil: m₁v₁ = m₂v₂. The heavier object moves slower.
Equation usedMomentum and impulse
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