An object shaped as a hemisphere rests with its flat surface on a table. The object has radius rand densityρ.rtableThe volume of a sphere is 34 πr 3 .Which average pressure does the object exert on the table?A 31ρ r 2 B 31ρ r 2g C 32ρ r D 32ρ rg
Question
An object shaped as a hemisphere rests with its flat surface on a table. The object has radius rand densityρ.rtableThe volume of a sphere is 34 πr 3 .Which average pressure does the object exert on the table?A 31ρ r 2 B 31ρ r 2g C 32ρ r D 32ρ rg
Solution
The average pressure an object exerts on a surface is given by the formula:
Pressure = Force / Area
The force exerted by the object is its weight, which is given by:
Weight = Mass * g
The mass of the object can be found by multiplying its volume by its density. For a hemisphere, the volume is half that of a sphere, so:
Volume = 1/2 * 4/3 * π * r^3 = 2/3 * π * r^3
So, the mass is:
Mass = Volume * Density = 2/3 * π * r^3 * ρ
Substituting this into the formula for weight gives:
Weight = 2/3 * π * r^3 * ρ * g
The area over which this force is distributed is the area of the flat surface of the hemisphere, which is a circle of radius r. So:
Area = π * r^2
Substituting the expressions for weight and area into the formula for pressure gives:
Pressure = (2/3 * π * r^3 * ρ * g) / (π * r^2) = 2/3 * r * ρ * g
So, the average pressure the object exerts on the table is 2/3 * r * ρ * g, which is closest to option D: 32ρ rg.
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