Question

A person on the street wants to throw an 8kg book up to a person leaning out of a window 5m above street level.With what velocity must the person throw the book so that it reaches the person in the window?

Answer 1

\[v ^{2}-u ^{2}=2ad\]
\[0-u ^{2}=2(-9.8)(5)\]
\[u=\sqrt{98}\]
here mass has no role since it is kinematics

Answer 2

i think a better view is by conserving energy.. to reach 5m above the book MUST have a min. potential energy of mgh. so it must be thrown with a velocity of at least v, such that 1/2*mv^2 = mgh.