Question

A ball falls on surface from $10m$ height and rebounds to $2.5m$. If duration of contact with floor is $0.01sec$ then average acceleration during contact is____________$m{s}^2$

• A. $2100$
• B. $1400$
• C. $707$
• D. $400$

Answer 1

The correct option is C $707$

We know velocity of the ball when dropped from a height $h=10m$

$v_1=\sqrt{2gh}=\sqrt{2\times 10\times 10}=10\sqrt{2}$

and velocity of the ball when rebounds to a height of $h=2.5m$

$v_2=\sqrt{2\times 10\times 2.5=5\sqrt{2}}$

Now we know acceleration $a=\frac{v_1-v_2}{t}$

here t= 0.01 s

$a=\frac{10\sqrt{2}-5\sqrt{2}}{0.01}=707$