Calculate the change in pressure in the following cases.

1. When the force acting on the area is doubled, while the area is doubled.

2. When the force acting on the area is halved, while the area is halved.

A block of wood having a mass $15 \mathrm{kg}$ and dimensions $40\mathrm{cm} \times 30\mathrm{cm} \times 20 \mathrm{cm}$ is kept on a table-top, It is made to lie on the table-top in three ways with its sides of dimensions

(a) $40 \mathrm{cm} \times 30 \mathrm{cm}$

(b) $30 \mathrm{cm} \times 20 \mathrm{cm}$

(c) $20 \mathrm{cm} \times 40 \mathrm{cm}$
 

The pressure exerted by the wooden block on the table-top will be

State whether upthrust will increase or decrease if the volume of the solid increases.

Give reasons: A body experiences more buoyant force on the earth than on the moon.

Give reasons: It is easier to swim in the sea than in the river.