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C) A buliet having a mass of 10 g andmoving with a speed of 1.5 m/s,penetrates a thick wooden plank ofmass 900 g. The plank was initiallyat rest. The bullet gets embedded inthe plank and both move together.Determine their velocity.(Ans: 0.15 m/s)d) A person swims 100 m in the first40 s, 80 m in the next 40 s and 45 min the last 20 s. What is the averagespeed?(Ans: 2.25 m/s2) |
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Answer» Answer: (C) mass of bullet=10g=0.01kg velocity of bullet=1.5 s m mass of plank=90g=0.09kg Total MOMENTUM before collision=mass of plank × velocity =0.01×1.5+0.09×0=0.015kg s m Total momentum after collision=(mass of bullet +mass of plank )× velocity =0.1kg×V=0.1Vkg s m According to law of conservation of momentum, Total momentum before collision=Total momentum after collision 0.015kg s m =0.1vkg s m velocity ACQUIRED by the plank and the bullet=0.15 s m. |
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