A block of wood is kept on a table top The mass of the wooden block is 5 kg and its dimensions are `40cmxx20cmxx10cm`. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table with its sides of dimension (a)`20cmxx10cm`(b) `40cmxx20cm`. Given`g=9.8(m)/(s^2)`.

Explanation

the mass of the wooden block =5 kg
the dimensions
`=40 cm xx 20 cm xx 10 cm `
Here , the weight of the wooden block applies a thrust on the table top .
that is
Thrust `= F = mxxg`
`=5 kg xx9.8 m s^(-2)`
=49 N
Area of side = length`xx` breadth
`=20 cm xx 10 cm `
`=200 cm ^(2) = 0.02 m^(2)`
From Eq .(10.20)
Pressure `=(49)/( 0.02 m^(2)) `
`= 2450 N m^(-2)`
when th block lies on its side of dimensions `40 cm xx20 cm ` it exerts the same throust
Aera = length `xx` breadth
`=40 cm xx20 cm`
`=800 cm ^(2) = 0.08 m^(2)`
From Eq .(10.20) ,
pressure `=(49) /(0.08 m^(2))`
=612.5 ` N m^(-2)`
the pressure ecerted by the side` 20 cm xx 10 cm ` is ` 2450 N m^(2) ` and by th side `40 cm xx 20cm ` is 612.5 `N m ^(-2)`