### Theory:

1. A fielder in the cricket ground pulls his hands backwards with the fast-moving cricket ball during the action of catching. By this action, the fielder prolongs the time to decrease the velocity of the fast-moving ball to zero. Hence, the impact of catching the fast-moving ball is reduced by decreasing the acceleration of the ball.

If the fielder suddenly stops the ball, its high velocity drastically decreases to zero in a very short period.

As a result, the rate of change of momentum will be large, and thus, a large force should be exerted for taking the catch that may hurt the fielder's palm.

2. Athletes in high jump sporting events are forced to land on a cushioned or a sand bed. This is done to prolong the time it takes for the athlete's fall to come to a halt after completing the jump. An increase in the time of fall reduces the force by lowering the rate of change of momentum.

3. With the same technique, a karate player breaks an ice slab with a powerful single blow.

From the second law's mathematical expression, the first law of motion can be easily stated.

$\begin{array}{l}F\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}m\phantom{\rule{0.147em}{0ex}}a\\ \\ F\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}\frac{m\phantom{\rule{0.147em}{0ex}}\left(v-u\right)}{t}\\ \\ \mathit{Ft}\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}m\phantom{\rule{0.147em}{0ex}}v-m\phantom{\rule{0.147em}{0ex}}u\end{array}$

When the force $$F$$ is zero, the final velocity is equal to the initial velocity ($$v =u$$), whatever the time $$t$$ may be.

Hence, it implies that the object will continue its motion with uniform velocity, $$u$$ throughout the time, $$t$$. If $$u$$ is zero, then $$v$$ will also be zero, keeping the object at rest.
Reference:
https://image.shutterstock.com/z/stock-photo-barcelona-july-european-athletics-championships-barcelona-decathlon-high-jump-in-the-58176451.jpg - Photography by Natursports