A particle of mass 2mis dropped from a height 80 m above the ground. At the same time another particle of mass m is thrown vertically upwards from the ground with a speed of 40 m/s. If they collide head-on completely inelastically, the time taken for the combined mass to reach the ground, in units of second is:

A particle of mass 2mis dropped from a height 80 m above the ground. A

1.	A particle of mass 2mis dropped from a height 80 m above the ground. At the same time another particle of mass m is thrown vertically upwards from the ground with a speed of 40 m/s. If they collide head-on completely inelastically, the time taken for the combined mass to reach the ground, in units of second is:
Answer» `((sqrt(112) - 2)/(3))` `((sqrt(80) - 2)/(3))` `((sqrt(105) - 2)/(5))` `((sqrt(112) + 2)/(5))` Solution :Particles will collide after time `t_(0) = (80)/(40) = 2sec.` at COLLISION , `v_(A) = 20v_(B = -20` Velocity of combined mass = `(2m xx 20 - m xx 20)/(2m + m) = (20)/(3) m//s` Time taken by combined mass to REACH the ground Time = `((sqrt(112) - 2)/(3))`SEC.

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