An ace footballer converted a penalty shot by kicking the football with a speed of 108 km h⁻¹. The estimated force they imparted was 800 N. The mass of the football was 0.4 kg. Calculate the time of contact between their foot and the ball.

Given, $v = 108\text{ km h}^{-1}$

$$= \frac{108 \times 1000}{3600} = 30\text{ ms}^{-1}$$

$$m = 0.4\text{ kg}, F = 800\text{ N}, u = 0\text{ ms}^{-1}$$

Force applied, $F = 800\text{ N}$

Initially, the football is at rest

$$u = 0$$

Using Newton's second law

$$F = \frac{m(v-u)}{t}$$

$$800 = \frac{0.4(30-0)}{t}$$

$$800 = \frac{12}{t} \Rightarrow t = \frac{12}{800}$$

$$t = 0.015\text{ s}$$

Therefore, the time of contact between the football and the player's foot is 0.015 s.