A body is at aheight of 81m and is ascending upwards with a velocity of 12m/s. a body of 2 kg weight is dropped from it. if g=10m/s^2. the body will reach the surface if earth in how much time.

First the velocity drops to zero in 1.2 secs. In those seconds it went upwards for 7.2 m, then it went from 87.2 to 0m. x-x0=v0*t+1/2*g*t^2 ergo t=sqrt (2x/g) that is 4.1761 s. Finally the total time required is 5.3761 s