Force and pressure

11.1 Pressure and surfaces

• Pressure is caused when objects exert forces on each other, or when a fluid exerts a force on an object in contact w/ the fluid. Size of pressure depends on the area of contact on which the forces act and the size of the force
• pressure (pascals, Pa) = force (N) / area (m^2)
• Knives must be sharp so that there is a smaller area of contact and a larger pressure, so less force needs to be exerted

11.2 Pressure in a liquid at rest

• The pressure of a liquid increases with depth.
• The further the hole is below the level of water in the bottle, the greater the force w/ which the jet leaves the bottle because the water pressure increases as the holes get further down the bottle
• Pressure in a liquid depends on the density of the liquid. Oil's less dense than water so water is below oil. 
• pressure, p (Pa) = height, h (m) x density, p (m^3) x gravity, g (N/Kg)

11.3 Atmospheric pressure

• Atmospheric pressure is due to air molecules colliding w/ surfaces. Each impact exerts a tiny force on the surface, but the no. of molecules that…