MCQ
A $40\ g$ ball dropped from a certain height bounces back from the horizontal ground without losing mechanical energy. If its speed is $10\ m/s$ just before making contact with the ground, and the average value of the force of the ground on the ball is equal to $16\ N$ while ball and wall are in contact, how long were they in contact .......... $m/s$ 
  • A
    $25$
  • $50$
  • C
    $75$
  • D
    $100$

Answer

Correct option: B.
$50$
b
$\begin{gathered}
  2 \times 40 \times {10^{ - 3}} \times 10 = 16\,t \hfill \\
  50 \times {10^{ - 3}}\,s\, = \,t \hfill \\ 
\end{gathered} $

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