[Density and Pressure]

Question 1

43. Density

Answer 1

ρ. Mass per unit volume. Measured in metres cubed, m3. ρ = m / V.

Question 2

44. Pressure (in Liquids)

Answer 2

p. Force per unit area. Measured in Pascals, Pa or Nm-2. p = F / A.
Or in a liquid in a vertical column: p = h ρ g.
p = pressure (Pa); h = height (m); ρ = density (m3); g = gravitational field strength (Nkg-1).

Question 3

45. Upthrust on an Object in Fluid

Answer 3

U. The upward buoyant force exerted on a body immersed in a fluid (liquid or gas).
Equal to the weight of the displaced fluid. The object will float if W OBJECT = U or sink if W OBJECT > U. U = ρ V g. U = upthrust (N); ρ = density of fluid (kgm-3); V = volume of displaced fluid (m3); g = gravitational field strength (Nkg-1).

Question 4

46. Archimedes’’ Principle

Answer 4

The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.