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# A juggler is maintaining four balls in motion, making each in turn to rise to height of 20 m. With what velocity does he project them ?

$\begin{array}{1 1}(A)\;30ms^{-1}\\(B)\;20ms^{-1} \\(C)\;9 ms^{-1} \\(D)\;67 ms^{-1} \end{array}$

$v^2= u^2+2ah$
Gives on putting $v=0,h=20m,a=-g=-10ms^{-2}$
$0=u^2-2 \times 10 \times 20 ,u= 20 ms^{-1}$
Hence B is the correct answer.