Density, Pressure & Upthrust Flashcards
What’s the definition of density?
Mass per unit volume
What is the equation for density? (Include units)
Density (p) =m/v
Units:kgm^-3
State 2 factors that affect the density of an object or substance
- The type of atoms present in a substance (atomic masses)
- how lightly packed the atoms are (solid/liquid/gas) (particle arrangement)
What’s the definition of pressure?
Force per unit area
What’s the equation of pressure? (Include units)
P=f/a
Units: Pa or Nm^-1
Why do all objects placed in a fluid experience pressure?
Due to the constant collisions between the particles in the fluid & the surface of the object experiencing the pressure
What is meant by the term fluids?
Liquids and gases
What factors affect the pressure exerted when an object is placed in a fluid?
Weight/force exerted on the object & the cross sectional area
What’s the equation for fluid pressure?
P = p(fluid density)hg
What is it important to note about fluid pressure in static fluids?
The fluid pressure is independent of the shape, total mass or surface area of the liquid
Explain why objects in a fluid experience upthrust
Upthrust occurs because the pressure acting on the underside of an object is always greater than the pressure acting on the top surface
What is upthrust?
An upward force that fluids exert on objects that are completely or partially submerged in the fluid
What’s the equation for upthrust?
Difference in pressure X surface area
(p(density) x g x change h)
What is Archimedes principle?
An object submerged or floating in a fluid experiences an upthrust equal to the weight of the fluid displaced
What’s the rule of thumb for displacement of floating objects?
If the density ofthe object is 90% the density of water, it will float with 90% of its mass below the water line and 10% above
