In 1654 Otto von Guericke, inventor of the air pump, gave a demonstration before the noblemen of the Holy Roman Empire in which two teams of eight horses could not pull apart two evacuated brass hemispheres. (a) Assuming the hemispheres have (strong) thin walls, so that R may be considered both the inside and outside radius, show that the force required to pull apart the hemispheres has magnitude F = pR2 p, where p is the difference between the pressures outside and inside the sphere. (b) Taking R as 30 cm, the inside pressure as 0.10 atm, and the outside pressure as 1.00 atm, find the force magnitude the teams of horses would have had to exert to pull apart the hemispheres. (c) Explain why one team of horses could have proved the point just as well if the hemispheres were attached to a sturdy wall.
Fluid Pressure
The term fluid pressure is coined as, the measurement of the force per unit area of a given surface of a closed container. It is a branch of physics that helps to study the properties of fluid under various conditions of force.
Gauge Pressure
Pressure is the physical force acting per unit area on a body; the applied force is perpendicular to the surface of the object per unit area. The air around us at sea level exerts a pressure (atmospheric pressure) of about 14.7 psi but this doesn’t seem to bother anyone as the bodily fluids are constantly pushing outwards with the same force but if one swims down into the ocean a few feet below the surface one can notice the difference, there is increased pressure on the eardrum, this is due to an increase in hydrostatic pressure.
In 1654 Otto von Guericke, inventor
of the air pump, gave a
demonstration before the noblemen
of the Holy Roman Empire in
which two teams of eight horses
could not pull apart two evacuated
brass hemispheres. (a) Assuming
the hemispheres have (strong) thin
walls, so that R may be considered both the inside
and outside radius, show that the force required to pull apart
the hemispheres has magnitude F = pR2 p, where p is the difference
between the pressures outside and inside the sphere.
(b) Taking R as 30 cm, the inside pressure as 0.10 atm, and the outside
pressure as 1.00 atm, find the force magnitude the teams of
horses would have had to exert to pull apart the hemispheres.
(c) Explain why one team of horses could have proved the
point just as well if the hemispheres were attached to a sturdy wall.
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