Calculate the magnitude of buoyant force

In summary, we have two cubes, a copper cube with a density of 8.96 g/cm3 and a lead cube with a density of 11.4 g/cm3, both with an edge length of 3.0 cm. We need to calculate the magnitude of the buoyant force acting on each cube when fully submerged in water. Since the density of water is 1g/cm^3, both materials are denser than water. The buoyant force is equal to the weight of water displaced by the object, and since both cubes have the same volume, they will displace the same amount of water, resulting in the same buoyant force.
  • #1
feelthebeat
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Consider two cubes: a copper cube (Density = 8.96 g/cm3 and a lead cube (Density = 11.4 g/cm3 that both have an edge length of 3.0 cm

Calculate the magnitude of the buoyant force (in Newtons) acting on the copper cube and the lead cube when each is fully submerged in water. Show your work.

Thanks in advance for any help!
 
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  • #2
Welcome to PF.

we know that the density of water is 1g/cm^3. Which means that we know both of these materials are much more dense than water.

Lets explore what buoyant force with respect to water is. The buoyant force is equal to the weight in water displaced by the object. Both of these objects are the same volume correct? so both of the objects displace the same amount of water, right? so their buoyant forces are...
 

1. What is buoyant force?

Buoyant force is a force exerted by a fluid on an object that is submerged or partially submerged in the fluid. It is a result of the pressure difference between the top and bottom of the object, with the greater pressure at the bottom pushing up on the object.

2. How is the magnitude of buoyant force calculated?

The magnitude of buoyant force is calculated using the formula Fb = ρVg, where Fb is the buoyant force, ρ is the density of the fluid, V is the volume of the displaced fluid, and g is the acceleration due to gravity. This formula is known as Archimedes' principle.

3. What factors affect the magnitude of buoyant force?

The magnitude of buoyant force is affected by the density of the fluid, the volume of the displaced fluid, and the acceleration due to gravity. It is also affected by the shape and size of the object submerged in the fluid.

4. How does buoyant force relate to an object's weight?

Buoyant force acts in the opposite direction to the weight of an object. If the buoyant force is greater than the weight, the object will float. If the weight is greater than the buoyant force, the object will sink.

5. Can buoyant force be negative?

No, buoyant force cannot be negative. It is always directed upwards and is a positive force. However, the net force on an object can be negative if the weight is greater than the buoyant force, causing the object to sink.

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