MCQ
Conservation of momentum in a collision between particles can be understood from:
- AConservation of energy.
- BNewton’s first law only.
- CNewton’s second law only.
- ✓Both Newton’s second and third law.
✓
Answer
Correct option: D.
Both Newton’s second and third law.
- By newton's second law $\frac{\vec{\text{dp}}}{\text{dt}}=\vec{\text{f}}_\text{ext}$
$\text{i.e},\vec{\text{f}}_\text{ext}=0$
$\frac{\vec{\text{dp}}}{\text{dt}}=0$
$\Rightarrow\vec{\text{p}}$ is constant.
- By netton's third law action force is equal to reaction force in magnitude but in opposite direction.
$\frac{\vec{\text{dp}_{12}}}{\text{dt}}=\frac{\vec{\text{- dp}_{21}}}{\text{dt}}$ or $\vec{\text{dp}_{12}}=-\vec{\text{dp}_{21}}$
$\vec{\text{dp}}_{12}+\vec{\text{dp}_{21}}=0.$
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