What pressure is exerted on the soil by a boy weighing 45 kg, who holds a watermelon weighing 7.5 kg in his hands, if the area of one of his soles is 150 cm2
m1 = 45 kilograms – the weight of the boy;
m2 = 7.5 kilograms – the mass of a watermelon that a boy is holding in his hands;
s = 150 cm2 = 0.015 m2 – the area of one boy’s sole;
n = 2 – total number of soles.
It is required to determine P (Pascal) – the pressure exerted by the boy on the soil.
Let’s find the total mass of the boy and the watermelon:
m = m1 + m2 = 45 + 7.5 = 52.5 kilograms.
Then the force of gravity will be equal to:
F = m * g (where g = 10 N / kg is an approximate value);
F = 52.5 * 10 = 525 Newton.
The total area of the soles will be equal to:
S = s * n = 0.015 * 2 = 0.03 m2.
Then the pressure will be equal to:
P = F / S = 525 / 0.03 = 17500 Pascal (17.5 kPa).
Answer: the boy exerts a pressure of 17.5 kPa on the soil.