2n identical cubical blocks are kept in a straight line on a horizontal smooth surface. The distance between the consecutive block is same . The block 1,3,5...(2n-1) are given velocity v to the right whereas blocks 2,4,6..,2n are given velocity to the left . All collisons between blocks are perfect elastic . The total number of collisons that will take place is?
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At first there will be n collisions, after that the first and the last blocks will move away from the other blocks, then there will be n − 1 collisions, and so on...
total number of collisions is
n + ( n − 1 ) + ( n − 2 ) + . . . + 1 = 2 n ( n + 1 )