Free JEE Main Physics COM of Discrete Mass Systems MCQs with step-by-step solutions (2 questions). Part of Centre of Mass, Momentum & Collisions. Practise online on Prepizo — no login needed.
Q1 — COM of Discrete Mass Systems · easy · numerical
The separation of H and Cl in an HCl molecule is r; Cl is ~35.5 times heavier than H. The COM lies:
A. Very close to H
B. Outside the molecule
C. At the middle
D. Very close to the Cl atom (≈ r/36.5 from Cl) ✓ Correct
Solution: x from Cl = m_H r/(m_H + m_Cl) = r/36.5 — practically on the chlorine atom.
Q2 — COM of Discrete Mass Systems · medium · numerical
Masses 1 kg, 2 kg, 3 kg, 4 kg sit at the corners A, B, C, D of a 1 m square (in order). Taking A at the origin with AB along x, x_cm equals:
A. 0.4 m
B. 0.6 m
C. 0.25 m
D. 0.5 m ✓ Correct
Solution: x: A=0, B=1, C=1, D=0 ⇒ x_cm = (0 + 2 + 3 + 0)/10 = 0.5 m.