# A boy with a mass of 45 kg stands on a square wooden block of 50 cm. How do you calculate the pressure exerted by the boy?

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### 2 Answers

Hello!

By definition, the pressure is the force divided by the area, on which force acts. In SI it is measured in pascals (`N/m^2` ).

In our case area is `50cm*50cm = 0.5m*0.5m = 0.25m^2` .

The force is the gravity one (probably we ignore the buoyancy force of air). This force is equal to m*g, where m is mass and g is gravity acceleration, `g=9.8m/s^2` .

So the pressure is

`45*9.8/0.25` = **1764(Pa)**.

**Sources:**

We know that

Pressure = Force / Area

Step 1: Calculation of Force

We know that Force = ma

= mass x acceleration due to gravity

Given that mass of the boy = 45 kg

we know that acceleration due to gravity = 9.8 m/s^2

Hence, Force = mass x acceleration due to gravity

= 45 kg x 9.8 m/s^2

= 441 N ( Newton, N= kg . m/s^2)

Step 2: Calculation of Area

Since boy is standing on the square wooden block , we have to calculate the area of the square wooden block .

Given that side of square wooden block = 50 cm

= 50 x 0.01 m (1 cm = 0.01 m)

= 0.5 m

Area of the square block = side x side ( area of square = side x side)

= 0.5 m x 0.5 m

= 0.25 m^2

Therefore, Area of square block = = 0.25 m^2

Step 3: Calculation of Pressure

Pressure = Force / Area

From step 1, Force = 441 N

From Step 2, Area = 0.25 m^2

Therefore,

Pressure = Force / Area

= 441 N/ 0.25 m^2

= 1764 N/ m^2

= 1764 Pa ( Pascal, Pa = N/m^2)

= 0.017 atm

{We know that 1 atm = 101325 Pa

Hence , 1764 Pa = 0.017 atm [(1764 Pa/ 101325 Pa) x 1atm ] = 0.017 atm) }

Therefore,