Question 13 — An ace footballer converted - Questions at the end of the chapter - Chapter 6 - How Forces Affect Motion (Exploration)

Speed = 108 km h ⁻¹ = \( 108 \times \dfrac{5}{18} = 30\ \text{m s}^{-1} \). The ball starts from rest, so u = 0, v = 30 m s ⁻¹ .

Acceleration \( a = \dfrac{F}{m} = \dfrac{800}{0.4} = 2000\ \text{m s}^{-2} \).

Using v = u + at: \( 30 = 0 + 2000\,t \), so \( t = \dfrac{30}{2000} = \mathbf{0.015\ s} \).