1. Density and Buoyant Force
Section 1 Fluids and Buoyant Force
Chapter 8
Density and Buoyant Force
The concentration of matter of an object is called the mass density.
Mass density is measured as the mass per unit volume of a substance.

2. Density is sort of a measurement of how much “stuff” (mass) is crammed into how much space (volume)
A golf ball and a ping pong ball have about the same volume, but a golf ball has more mass in the same amount of space, so it’s more dense

3. Density and Buoyant Force, continued
Section 1 Fluids and Buoyant Force
Chapter 8
Density and Buoyant Force, continued
The buoyant force is the upward force exerted by a liquid on an object immersed in or floating on the liquid.
Buoyant forces can keep objects afloat.

4. Buoyant Force and Archimedes’ Principle
Section 1 Fluids and Buoyant Force
Chapter 8
Buoyant Force and Archimedes’ Principle
Click below to watch the Visual Concept.
Visual Concept

5. Density and Buoyant Force, continued
Section 1 Fluids and Buoyant Force
Chapter 8
Density and Buoyant Force, continued
Archimedes’ principle describes the magnitude of a buoyant force.
Archimedes’ principle: Any object completely or partially submerged in a fluid experiences an upward buoyant force equal in magnitude to the weight of the fluid displaced by the object.
FB = Fg (displaced fluid) = mfg
magnitude of buoyant force = weight of fluid displaced

6. Chapter 8 Buoyant Force Section 1 Fluids and Buoyant Force
An object will
Float as long
As the buoyant force
Equals the force of gravity

7. Forces on an airplane

8. Forces on a hot air balloon

9. Chapter 8
Section 2 Fluid Pressure
Pressure
Pressure is the magnitude of the force on a surface per unit area.

10. Pressure Force is measured in N and area is measured in m2
1 N/m2 = 1 pascal (Pa)
When discussing air pressure, we sometimes use the
unit atm (atmospheres). It describes air pressure relative to sea level.