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 $F_b (= W_f = m_f g) = \rho_f V_f g$