1.
Acceleration due to gravity is 10 N/kg. The surface area of fish pressed by the water above it is 6 cm2. Determine the force of water above fish that acts on fish.
Known :
Acceleration due to gravity (g) = 10 N/kg
Surface area of fish (A) = 6 cm2 = 6 x 10-4 m2
Density of water = 1 gram/cm3 = 1 (10-3 kg) / 10-6 m3 = 103 kg/m3 = 1000 kg/m3
Height of water = 100 cm – 15 cm = 85 cm = 85 x 10-2 meters
Wanted : Force of the water above fish that acts on fish
Solution :
Equation of pressure:
P = F / A
F = P A
F = ρ g h A
F = (1000)(10)(85 x 10-2)(6 x 10-4 m2)
F = (104)(510 x 10-6)
F = 510 x 10-2
F = 5.1 Newton
2. The normal pressure of blood is 80 mm hg to 120 mm hg. This value is equal to…
A. 80 Pascal to 120 Pascal
B. 800 Pascal to 1200 Pascal
C. 10256 Pascal to 17589 Pascal
D. 10526 Pascal to 15789 Pascal
Known :
The normal pressure of blood = 80 mm Hg – 120 mm Hg
Wanted: This value is equal to… Pascal
Solution :
The height of mercury in a barometer (above the surface of the sea) = 760 mm Hg
Pressure of air (above the surface of sea) = 1 atm = 1.0 x 105 Pascal
1 mm Hg = ……. Pascal?
80 mm Hg = 80 x 131.58 Pascal = 10,526 Pascal
120 mm Hg = 120 x 131.58 Pascal = 15,789 Pascal
The correct answer is D.
3. Above the surface of the sea, the height of mercury in a barometer is 760 mm. If at a place, the height of mercury in a barometer is 700 mm. Determine the pressure of air at that place.
Known :
The height of mercury in a barometer (above the surface of the sea) = 760 mm Hg
Pressure of air (above the surface of sea) = 1 atm = 1,013 x 105 Pascal
Wanted: Determine the pressure of air if the height of mercury is 700 mm
Solution :
760 mm Hg = 1.013 x 105 Pascal
700 mm Hg = ……… Pascal?
