1. after striking the floor ,a ball rebounds 80% of the height from which it has fallen. find the total distance that it travels before coming to rest if it is dropped from a height of 120 cm.

Dear sougata

Total distance travel by ball is

S = 120 + 2*120*.8 + 2*120*(.8)²  + 2*120(.8)³ +.................∞

i have multiplied by 2 because ball travells two time first when ball move from flour to vertically upward and second when it come back  to flour.

S = 120 + 2*120*.8[ 1 + .8 + (.8)²+......∞]  in bracket we have infinite geometric progression

  =120 + 192[ 1/(1-0.8)]

  =120 + 192[5]

  =1080   cm

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