Buoyancy

Buoyancy Force

• The amount of upward buoyant force \(F_b\) on a submerged object in a fluid is: \(F_b = \rho_f V_f g\)
• \(\rho_f\): Density of the fluid
• \(V_f\): Volume of the fluid the object displaces
• \(g\): Gravitational acceleration
• Archimedes Principle: The buoyant force \(F_b\) is equal to the weight \(W_f\) of the fluid displaced
• Indeed, \(F_b = W_f = m_f g = \rho_f V_f g\)
• An object will float if the amount of buoyancy force \(F_b\) balances its weight \(W_o\): \(F_b = W_o\)

Remarks / Tips

• To calculate the amount of buoyant force, it is often easier to first check if \(W\) is available before using \(F_b (= W_f = m_f g) = \rho_f V_f g\)