Interesting Facts About Sharks' Buoyancy
How do sharks maintain their buoyancy in water?
Sharks are generally negatively buoyant; the upward buoyant force is less than the weight force. This is one reason sharks tend to swim continuously; water moving past their fins causes a lift force that keeps sharks from sinking. A 92 kg bull shark has a density of 1040 kg/m3. What lift force must the shark's fins provide if the shark is swimming in seawater? Bull sharks often swim into freshwater rivers. What lift force is required in a river?
Answer:
8.67807 N in seawater
34.7123 N in a river
Sharks tend to swim continuously because of their negative buoyancy. The lift force required can be calculated by multiplying the volume of the shark by the density of seawater and the acceleration due to gravity. The lift force required in a river can be determined using the density of freshwater.
Explanation:
Sharks tend to swim continuously because they are negatively buoyant, which means that the upward buoyant force is less than their weight force. However, the water moving past their fins generates a lift force that counteracts the tendency to sink. To calculate the lift force required, we need to determine the volume of the shark and multiply it by the density of seawater. Given that the density of the shark is 1040 kg/m3 and its mass is 92 kg, we can calculate its volume using the formula: V = m / ρ = 92 kg / 1040 kg/m3 = 0.088 m3
The lift force required can be determined by multiplying the volume by the density of seawater and the acceleration due to gravity: F = ρwater * g * V = 1030 kg/m3 * 9.8 m/s² * 0.088 m3 = 900 N
To calculate the lift force required in a river, we need to use the density of freshwater. Given that the density of freshwater is around 1000 kg/m3, we can plug this value into the formula: F = ρfreshwater * g * V = 1000 kg/m3 * 9.8 m/s² * 0.088 m3 = 860 N