Give reason: Trucks carrying a heavy load are fitted with additional wheels up to eight in number.

Give reasons: The wheels of army tanks roll over a wide steel belt fitted with wheels.

Calculate the pressure when a force of $100 \mathrm{N}$ acts perpendicular to a surface of area $10 {\mathrm{m}}^2$.

A $5 \mathrm{kg}$ wooden block is kept on top of a table. Its dimensions are $30 \mathrm{cm}\times 20 \mathrm{cm}\times 5 \mathrm{cm}$. Find the pressure exerted by the wooden block on the tabletop, if it is made to lie on the tabletop with its side of dimensions:$30 \mathrm{cm} \mathrm{x} 20 \mathrm{cm}$.      

A $5 \mathrm{kg}$ wooden block is kept on top of a table. Its dimensions are $30 \mathrm{cm}\times 20 \mathrm{cm}\times 5 \mathrm{cm}$. Find the pressure exerted by the wooden block on the tabletop, if it is made to lie on the tabletop with its side of dimensions: $30 \mathrm{cm}\times 5 \mathrm{cm}.$

Distinguish between the pressure exerted by a solid and that by a liquid.