Momentum and CollisionHardBloom L3
Question
In the figure shown the system is at rest initially. Two persons ‘A’ and ‘B’ of masses 40 kg each move with speeds v1 and v2 respectively towards each other on a plank lying on a smooth horizontal surface as shown in figure. Plank travels a distance of 20 m towards right direction in 5 sec. (Here v1 and v2 are given with respect to the plank). Then the possible condition(s) can be
Options
A.v1 = 0 m/s, v2 = 10 m/s
B.v1 = 5 m/s, v2 = 15 m/s
C.v1 = 10 m/s, v2 = 20 m/s
D.v1 = 2 m/s, v2 = 12 m/s
Solution
Sol. Velocity of plank w.r.t. ground = $\frac{20}{5}$ = 4 m/s right.
Pf = 0
⇒ 40 (v1 + 4) + 40(4 – v2) + 20 × 4 = 0
⇒ 40 (v1 – v2) + 320 + 80 = 0
⇒ v1 – v2 = – 10
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