PPT: Buoyancy & Floatation | Fluid Mechanics for Mechanical Engineering PDF Download

 Page 1


What Is Buoyancy Force
?When a body is immersed in fluid, an upward     
force is exerted by the fluid on the body.
?This upward force is equal to the weight of the 
fluid displaced by the body and is called the force 
of buoyancy. 
Page 2


What Is Buoyancy Force
?When a body is immersed in fluid, an upward     
force is exerted by the fluid on the body.
?This upward force is equal to the weight of the 
fluid displaced by the body and is called the force 
of buoyancy. 
What causes buoyant force?
• Buoyant force is the       force on an object 
exerted by the surrounding fluid.
• When an object pushes water, the water 
pushes back with as much force as it can.
• If the water can push back as hard, the object 
floats (boat).  If not, it sinks (steel).
Page 3


What Is Buoyancy Force
?When a body is immersed in fluid, an upward     
force is exerted by the fluid on the body.
?This upward force is equal to the weight of the 
fluid displaced by the body and is called the force 
of buoyancy. 
What causes buoyant force?
• Buoyant force is the       force on an object 
exerted by the surrounding fluid.
• When an object pushes water, the water 
pushes back with as much force as it can.
• If the water can push back as hard, the object 
floats (boat).  If not, it sinks (steel).
Forces Acting on Buoyancy
• The buoyant force is caused by the difference 
between the pressure at the top of the object 
(gravitational force), which pushes it 
downward, and the pressure at the bottom 
(buoyant force), which pushes it upward
• Since the pressure at the bottom is always 
greater than at the top, every object 
submerged in a fluid feels an upward buoyant 
force. 
Page 4


What Is Buoyancy Force
?When a body is immersed in fluid, an upward     
force is exerted by the fluid on the body.
?This upward force is equal to the weight of the 
fluid displaced by the body and is called the force 
of buoyancy. 
What causes buoyant force?
• Buoyant force is the       force on an object 
exerted by the surrounding fluid.
• When an object pushes water, the water 
pushes back with as much force as it can.
• If the water can push back as hard, the object 
floats (boat).  If not, it sinks (steel).
Forces Acting on Buoyancy
• The buoyant force is caused by the difference 
between the pressure at the top of the object 
(gravitational force), which pushes it 
downward, and the pressure at the bottom 
(buoyant force), which pushes it upward
• Since the pressure at the bottom is always 
greater than at the top, every object 
submerged in a fluid feels an upward buoyant 
force. 
Keep It Simple
• Buoyancy= “the floating force”
• Water is “heavier” than the object…so the 
object floats
• Low density-more likely to float
• Buoyant force is measured in Newtons (N)
Page 5


What Is Buoyancy Force
?When a body is immersed in fluid, an upward     
force is exerted by the fluid on the body.
?This upward force is equal to the weight of the 
fluid displaced by the body and is called the force 
of buoyancy. 
What causes buoyant force?
• Buoyant force is the       force on an object 
exerted by the surrounding fluid.
• When an object pushes water, the water 
pushes back with as much force as it can.
• If the water can push back as hard, the object 
floats (boat).  If not, it sinks (steel).
Forces Acting on Buoyancy
• The buoyant force is caused by the difference 
between the pressure at the top of the object 
(gravitational force), which pushes it 
downward, and the pressure at the bottom 
(buoyant force), which pushes it upward
• Since the pressure at the bottom is always 
greater than at the top, every object 
submerged in a fluid feels an upward buoyant 
force. 
Keep It Simple
• Buoyancy= “the floating force”
• Water is “heavier” than the object…so the 
object floats
• Low density-more likely to float
• Buoyant force is measured in Newtons (N)
How do you Calculate B
F
?
Buoyant Force= Weight of displaced fluid
OR
B
F
=   W
air
- W
water
Buoyant     =   Weight of         - Weight of object 
Force               object in air in water