A ball is thrown vertically upwards with a velocity of 50 m/s. calculate (a) the maximum height to which it rises.
(b) the total time it takes to return to the surface of earth. (take g =10 m/s2 )

Given, For a vertically thrown upward,

          Initial velocity (u) = 50m/s

          Final velocity (v) = 0m/s { ∵ the body is thrown vertically upward }

          Acceleration due to gravity(a) = -(g)= -10m/s²

          Height reached (h) = ? , Time taken (t) = ?

We know that,v² = u²+2as

           or,        0² = (50)²+2×(-10)×h      { ∵ s=h }

           or,        0   = 2500+(-20h)

           or,        0   = 2500-20h

           or,        20h  = 2500

           or,        h   =

                  ∴     h   = 125metres

Also,       v  =  u + at

      or,    0  =  50+(-10)×t

      or,    0  = 50-10t

      or,    10t = 50

      or,    t   =

              ∴   t   = 5seconds   ANS

Hence, The height reached by the ball is 125m and time taken is 5secs.

they start with the same

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.