The correct option is A 100 m/s
Given that both the stones are thrown from same point.
Taking the upward direction as positive and downward as negative.
For first stone: When this stone reaches at highest point, its final velocity becomes zero i.e. v=0 and g=−g, u=50m/s, time at highest point = th
From first equation of motion v=u+at
Substituting the values, we get 0=50−gth ⇒th=5 s(∵g=10 m/s2)
For second stone: u=−50 m/s,
From first equation of motion
v=u+at
Substituting the values, we get,
v=−50−10×th
v=−100 m/s
−ve sign shows that v will be downward.