Answer
$2100\ N$
Work Step by Step
The mass of the ball $m=1.2\ kg$
Speed at which hits the ground $v_i = -25\ m/s$
Rebound speed $v_f = 10\ m/s$
Contact time $t =0.020\ s$
Relation between impulse and force is $J=F(\Delta t)$. Substituting and solving for $F$ yields:
$F = \frac{J}{\Delta t}$
$F = \frac{42\ kg.m/s}{0.02\ s}$
$F=2100\ N$
