A body of mass 100 g moving at 10 m/s collides and rebounds with a speed of 2 m/s. Calculate the change in momentum.

Given mass $m = 100 \text{ g}$.

Let the initial direction of motion be positive.
Initial velocity $v_i = 10 \text{ m/s}$.
After collision, the body moves in the opposite direction, so the final velocity is negative.
Final velocity $v_f = -2 \text{ m/s}$.

Momentum is given by $p = mv$.

The change in momentum is the final momentum minus the initial momentum.

The magnitude of the change in momentum is $1.2 \text{ kg m/s}$. The negative sign indicates the change is in the direction opposite to the initial motion.