Buoyancy

• Buoyancy is the upward force of a fluid exerted upon an object submerged in the fluid
• Buoyancy is a property of all fluids
• The buoyant force acts against the downward force of gravity (weight)
• The buoyant force acting on an object is equal to the weight of the fluid displaced by the object
• Buoyant force is an upward force exerted by a fluid, measured in Newtons (a Newton is a unit of force)
• Buoyant force = weight of object in air (N) - weight of object in fluid
• The Archimedes’ Principle states that the buoyant force on an object immersed in a fluid is equal to the weight of the fluid that the object displaces
• How do we know if something will sink or float?

  • If the buoyant force of an object is greater than the force of gravity on an object, it will float or rise or have positive buoyancy.
  • If the buoyant force of an object is less than the force of gravity on an object, it will sink or have negative buoyancy
  • If the two forces are equal, the object will not move up or down or will have neutral buoyancy and remain level in the fluid.
  • These properties also apply to objects in air, example helium balloons