Center of Mass, Momentum & Collision

JEE Main level, single correct, medium

106 of 130

Question 106 of 130

Blocks of masses m,2m,4m\text{m}, 2\text{m}, 4\text{m} and 8m8\text{m} are arranged in a line of a frictionless floor. Another block of mass mm , moving with speed υυ along the same line (see figure) collides with mass mm in perfectly inelastic manner. All the subsequent collisions are also perfectly inelastic. By the time the last block of mass 8m8\text{m} starts moving the total energy loss is \text{p%} of the original energy. Value of ‘p\text{p} ’ is close to:

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Answer: (B) 9494


Inelastic collision

mv=16mv1mv=16 {mv}^{1}
ΔKloss=12mv2−12(16M)(v16)2\Delta K loss=\dfrac{1}{2}{mv}^{2}-\dfrac{1}{2}\left(16M\right){\left(\dfrac{v}{16}\right)}^{2}
=12mv2−12Mv216=\dfrac{1}{2}{mv}^{2}-\dfrac{1}{2}M\dfrac{{v}^{2}}{16}
=12mv2(1516)=\dfrac{1}{2}{mv}^{2}\left(\dfrac{15}{16}\right)
%\Delta K loss=\dfrac{\dfrac{1}{2}{mv}^{2}\left(\dfrac{15}{16}\right)}{\dfrac{1}{2}{MV}^{2}}\times 100=\dfrac{15}{16}\times 100=93.75%

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