Question

Air pressure is roughly 100,000 Pa. What force is exerted on a book of area 0.035 m^2 when it is sitting flat on a table? What force is exerted on a cup coaster with diameter 5 cm?

Answer 1

Air pressure = P = 100000 Pa

Area of the book = A₁ = 0.035 m²

Force exerted on the book = F₁

F₁ = PA₁

F₁ = (100000)(0.035)

F₁ = 3500 N

Diameter of the cup coaster = D₂ = 5 cm = 0.05 m

Area of the cup coaster = A₂

A₂ = D₂²/4

A₂ = (0.05)²/4

A₂ = 1.963 x 10^-3 m²

Force exerted on the cup coaster = F₂

F₂ = PA₂

F₂ = (100000)(1.963x10^-3)

F₂ = 1963 N

A) Force exerted on the book = 3500 N

B) Force exerted on the cup coaster = 1963 N