Question

1. A boy weighs 50 N. The area of contact between his two feet is 10 cm². What pressure does he exert on the ground if he stands on one foot?
2. A man weighs 250 N. Suppose he stands on a pointed edge with a base area 5 cm². How much pressure does he exert on the ground?
3. Now compare (a) and (b) to find out the following.

1. Who exerts more force on the ground, the boy in (a) or the man in (b)?
2. Who exerts greater pressure on the ground, the boy or the man?
3. Who is likely to sink into the ground, the man standing on a pointed edge or the boy standing on one foot and why?

Answer 1

Part (a):

Step 1: Given data

Area (A) of two feet = $10cm²$

Force (F) = $50N$

Area (A) of one foot = $5cm²=\frac{5}{10000}{m}^2$

Area of one foot = $0.0005m²$

Step 2: Formula used and calculation

$Pressure\left(P\right)=\frac{Force\left(F\right)}{area\left(A\right)}$

Putting all the values we have,

$$\begin{gathered} P=\frac{F}{A} \\ P=\frac{50}{0.0005} \\ P=100000Pa. \end{gathered}$$

Hence, The pressure exerted by a boy on one foot is $100,000Pa$.

Part (b):

Step 1: Given data

Force (F) = $250N$

Area (A) of one foot =$5cm²=\frac{5}{10000}{m}^2$

A = $0.0005m²$

Step 2: Formula used and calculation

$Pressure\left(P\right)=\frac{Force\left(F\right)}{area\left(A\right)}$

Putting all the values we have,

$$\begin{gathered} P=\frac{F}{A} \\ P=\frac{250}{0.0005} \\ P=500000Pa. \end{gathered}$$

Hence, the pressure exerted by man on one foot is $500,000Pa$.

Part (c):

1. The man exerts more force on the ground.
2. The man exerts greater pressure on the ground.
3. The man standing on the edge is more likely to sink because more is the force, and more will be the pressure for the same area.