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: $30 \mathrm{cm}\times 5 \mathrm{cm}.$

Give reasons: A body weighs more in air than in a liquid.

Give reasons: A sphere of iron and another of wood (of the same radius) when held under water experience the same buoyant force.