A block of wood is kept on a table top. The mass of wooden block is 5kg and its dimensions are `40cm xx 20cm xx 10cm.` Find the pressure exerted by the wooden block on the table top if it is made to lie on the table top with its sides of dimensions (a) `20 cm xx 10cm and (b) 40cm xx 20cm`.

Explanation

The mass of the wooden block m=5kg
The dimensions `=40cm xx 20cm xx10cm`
(a) Here, the weight of the wooden block applies a thrust on the table top.
Thrust `F=m xx g`
`=5kg xx 9.8ms^(-2)`
=49N
Area of the side =length `xx` breadth
=20cm xx10cm
`=200cm^(2)`
`=0.02m^(2)`
Pressure `=(49N)/(0.02m^(2))`
(b) When the block lies on its side of dimensions `40cm xx 20cm`, it exerts the same thrust.
Area `="length "xx " breadth"`
`=40 cm xx20cm`
`=800cm^(2)`
`=0.08m^(2)`
Pressure `=(49N)/(0.08Nm^(-2))`
`=612.5Nm^(-2)`
The pressure exerted by the side `20 cm xx 10cm` is `2450Nm^(-2)` and by the side `40cm xx 20cm` is `612.5Nm^(-2)`.