# Archimedes' Principle

1. A copper penny has a mass of 2.7 g. What is the buoyant force acting on this penny when dropped into water? (The answer should be 3.0 mN)

2. An iceberg (917 kg/m^3) is floating in the ocean (1,025 kg/m^3). What percentage of the total volume of the iceberg is below the surface of the water? (The answer should be 89.5%)

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## SOLUTION This solution is **FREE** courtesy of BrainMass!

1. The buoyent force acting on the penny is equal to the weight of water displaced by the penny. Since copper has a specific gravity of S = 9.0, the mass of water displaced by the penny is

m_w = m_p/S

= 2.7 g / 9.0

= 0.3 g.

Thus, the buoyancy of the penny is

F_b = m_w g

= (0.3 g) (9.8 m/s^2)

= 2.9 g m/s^2

= 2.9 mN.

2. The mass of water displaced by the iceberg is equal to the total mass of the iceberg. Thus we have

m_w = m_i

d_w V_w = d_i V_i

V_w/V_i = d_i/d_w

= (917 kg/m^3)/(1,025 kg/m^3)

= 0.895.

= 89.5%.

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