How much pressure will a boy of wieght 50 kg f exert on the ground when (i) he is lying on ground and (ii) he is standing on his feet ? It is given that the area of the body of the boy is `0.5 m^2` and that of foot is `60 cm^2`. Use ` g = 10 m//s^2.`

Answer

(i) `1000 Nm^(-2)` (ii) `4.17 xx 10^4 Nm^(-2)`

Explanation

Here, `F = 50 kg f = 50xx10 = 500 N` (i) When boy is in the lying position, then `A = 0.5 m^2`
`P = (F)/(A) = (500N)/(0.5m^2) = 1000 Nm^(-2)` (ii) When boy is standing on his feet, then `A = 2xx60 cm^2 = 120xx10^(-4) m^2`
`P = (500N)/(120xx10^(-4)m^2) = 4.17 xx 10^4 Nm^(-2)`