4.5.5.1.2

4.5.5.1.2 Pressure in a fluid 2 (HT only)

4.5.5.1.2 Pressure in a fluid 2 (HT only)

Content

The pressure due to a column of liquid can be calculated using the equation:

[p=hρg]

pressure, p, in pascals, Pa

height of the column, h, in metres, m

density, ρ, in kilograms per metre cubed, kg/m3

gravitational field strength, g, in newtons per kilogram, N/kg (In any calculation the value of the gravitational field strength (g) will be given.)

Students should be able to explain why, in a liquid, pressure at a point increases with the height of the column of liquid above that point and with the density of the liquid.

Students should be able to calculate the differences in pressure at different depths in a liquid.

A partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface. This creates a resultant force upwards. This force is called the upthrust.

Students should be able to describe the factors which influence floating and sinking.

WS 4.3 Use SI units (eg kg, g, mg; km, m, mm; kJ, J) and IUPAC chemical nomenclature unless inappropriate.

WS 4.4 -Use prefixes and powers of ten for orders of magnitude (eg tera, giga, mega, kilo, centi, milli, micro and nano).

WS 4.5 - Interconvert units.

WS 4.6 - Use an appropriate number of significant figures in calculation.

MS 3b Change the subject of an equation

MS 3c Substitute numerical values into algebraic equations using appropriate units for physical quantities

MS 1c - Use ratios, fractions and percentages

MS 3c Substitute numerical values into algebraic equations using appropriate units for physical quantities

Resources

Pressure F

Pressure F ANS

Pressure H

Pressure H ANS

Depth T

Pressure T ANS

Video

SpikeySkateboard.mp4

Force and area

5wBGIHIE2IiZzsdW.mp4

How deep the oceon is

Practicals

Demo:

• Balloon
• Nail / pin
• Bed of nails

Safety

Sharp pins/nails careful of pushing balloon down on them