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Q4.17: NCERT Physics - Part 1 LAWS OF MOTION 4.17 Solution: A nucleus is at rest in the laboratory frame of reference. Show …
⚠️ Common Exam Traps & Conceptual Pitfalls
Students often treat the equation $\sum \vec p =0$ as if each individual momentum must be zero, concluding the fragments stay at rest. Remember that momentum is a vector; the correct condition is $\vec p_1+\vec p_2=0$, which means $\vec p_1=-\vec p_2$, i.e., equal magnitude and opposite direction, not zero magnitude for each.
A nucleus is at rest in the laboratory frame of reference. Show that if it disintegrates into two smaller nuclei the products must move in opposite directions.
Step-by-Step Verified Solution
**Answer:** By conservation of momentum, the two products must have equal and opposite momenta, hence they move in opposite directions.
**Step-by-Step Explanation:**
Initial momentum = 0 (nucleus at rest).
Let the products have masses m_ and m_ with velocities v_ and v_.
By conservation of momentum:
The negative sign indicates opposite directions [citation:10].
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