What force is applied on a piston of area of cross section 2 cm ² to obtain a force 150 N on the piston of area of cross section 12 cm ² in a hydraulic machine ?

The thrust exerted per unit area on the earth's surface due to a column of air is called :

1. pressure
2. atmospheric pressure
3. density
4. buoyancy

The unit torr is related to the barometric height as:

1. 1 torr = 1 cm of Hg
2. 1 torr = 0.76 cm of Hg
3. 1 torr = 1 mm of Hg
4. 1 torr = 1 m of Hg

The atmospheric pressure at earth surface is P₁ and inside mine is P₂. They are related as:

1. P₁ = P₂
2. P₁ > P₂
3. P₁ < P₂
4. P₂ = 0