Pressure, archimedes principle

PY1010 semester 1

Pressure

P = F/A

At depth h in a fluid of constant density, pressure exerted is

P = pgh

Total pressure at depth h in a fluid which is at earth’s surface

Ptotal = Patm +pgh

Explain: at earths surface, 1 atmosphere of pressure always exerted

Total pressure at any point in fluid (Pascal’s principle)

P = Patm + pgh

Hydraulic lift relations

1. Relation btwn how much force applied to one side of lift vs how much exerts on other: F1/A1 = F2/A2

2. If fluid is in-compressible, change in volume by pushing piston 1 down = change in vol that piston 2 moves thru. V1 = V2

Archimedes principle

When a body is completely/ partially immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid displaced by the body.

Fbouy = m_flg

1. Fbouy > Ws

2. Fbouy < Ws

3. Fbouy = Ws