5.6

5.6

07 October 2011

10:40
· 5.6 recall and use the relationship for pressure difference:

pressure difference = height × density × g

∆p = h × ρ × g

∆p = pressure of the fluid (N/m2 or Pa)

h = height of the fluid (m)

ρ = density of the fluid (kg/m3)

g = gravitational field strength (N/kg)

5.6 Demo - squirting water column

12 October 2011

07:24

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· The bottom hole squirts water the furthest
· Because the water at the bottom has the greatest pressure
· Because in the formula ∆p = h × ρ × g, ρ is constant, g is constant and h is large
· So ∆p = large

5.6 Questions

07 October 2011

11:53

Collins, p.107

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Notes:

ρfresh water = 1,000kg/m3

g = 10N/kg

1,000mbar = 1 bar = 100,000Pa

Q5) ∆p = h × ρ × g 250000- 100000 = h x 1000 150000 = h x 1000 x 10
150000/ 1000 = 15m

Q6) ∆p = h × ρ × g
∆p = 50 x 420 (0.42x 1000 to change it into kg/m3) x 1.4
∆p = 294000Pa
1,000mbar = 1 bar = 100,000Pa so 1,600mbar = 1.6 bar = 160,000Pa
29,400+160,000 = 189,400Pa TOTAL PRESSURE = 189,400Pa or 189.4 kPa

5.6 Plenary

12 October 2011

07:23
· Which diver experiences the greatest pressure?

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∆p = h × ρ × g
They both experience the same amount of pressure because the height is the same and we assume that the density and the gravitational field strength will be the same in the 2 places.

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