A child jumps straight down from a low platform

PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

25\,\text{kg}

child jumps straight down from a low platform, reaching the ground with a speed of

4.0\,\text{m/s}

. Four different playground surfaces are tested, each bringing the child to rest over the following vertical stopping distances: Surface A:

2.0\,\text{cm}

, Surface B:

5.0\,\text{cm}

, Surface C:

10\,\text{cm}

, Surface D:

15\,\text{cm}

. Rank the surfaces from greatest to least average force exerted on the child during the landing and briefly justify your ranking.