Mass
$\displaystyle \small \bullet$ Mass of a body is the quantity of matter contained in a body.
$\displaystyle \small \bullet$ Mass of a substance at a particular place remains constant.
$\displaystyle \small \bullet$ Units of Mass:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg$
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm$
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb$
Weight
$\displaystyle \small \bullet$ Weight is the force with which a body is attracted by the earth towards its centre.
$\displaystyle \small \bullet$ It is the product of the mass of the body and the acceleration due to gravity.
$\displaystyle \small \bullet$ Weight=mass × gravitational force
$\displaystyle \small W=mg$
$\displaystyle \small \bullet$ The weight of a body depends upon its location.
$\displaystyle \small \bullet$ Units of Weight:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg-m/sec^{2}$ or Newton
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm-cm/sec^{2}$ or Dyne
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb-ft/sec^{2}$ or Poundal
Density
$\displaystyle \small \bullet$ Mass per unit volume of a substance is called its density.
$\displaystyle \small Density=\frac{Mass}{Volume}$
$\displaystyle \small \bullet$ Units of Density:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg/m^{3}$
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm/cm^{3}$
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb/ft^{3}$
m - mass of a body
g - acceleration due to gravity in $\displaystyle \small m/sec^{2}$ = 9.81 $\displaystyle \small m/sec^{2}$
V - volume of the body
ρ - density (pronounced as `rho')
W or FG - weight or weight force
Relative Density/Specific Gravity
$\displaystyle \small \bullet$ It is the ratio of the density of a given substance to the density of water at 4$\displaystyle \small ^{0}C$.
Methods to find Relative Density
1. Archimedes principle
$\displaystyle \small \bullet$ Weight of body when immersed in liquid=Total weight of body - Weight of liquid displaced by body
To find Relative density of solid insoluble in water
To find Relative density of solid soluble in water
2. Using hydrometer
Nicholson Hydrometer: There is a hollow roller pin ‘A’ having hollow metallic cone ‘D’ joined at its bottom. The hydrometer is filled with wax or mercury to keep it balanced while floating in liquid. A thin rod ‘C’ is attached at the upper end of the roller pin. Point ‘B’, where the weights are to be placed.
To find Relative density of solid
To find Relative density of liquid
Laws of Floatation
$\displaystyle \small \bullet$ Assume,
$\displaystyle \small W_{1}$ = Weight of substance
$\displaystyle \small W_{2}$ = Weight of liquid displaced by substance
$\displaystyle \small \bullet$ If $\displaystyle \small W_{1}-W_{2}=0$, i.e. $\displaystyle \small W_{1}=W_{2}$ the weight of substance is equal to the upward thrust. Hence, the substance will float with difficulty.
$\displaystyle \small \bullet$ $\displaystyle \small W_{1}>W_{2}$ , the upward thrust is greater than the weight of the substance. Hence, the substance will rise in liquid till the weight of liquid displaced becomes equal to the weight of substance.
$\displaystyle \small \bullet$ If $\displaystyle \small W_{1}<W_{2}$ , the weight of the substance is greater than upward thrust. Hence, the substance will sink.
Specific Gravity of Substances
$\displaystyle \small \bullet$ Mass of a body is the quantity of matter contained in a body.
$\displaystyle \small \bullet$ Mass of a substance at a particular place remains constant.
$\displaystyle \small \bullet$ Units of Mass:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg$
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm$
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb$
Weight
$\displaystyle \small \bullet$ Weight is the force with which a body is attracted by the earth towards its centre.
$\displaystyle \small \bullet$ It is the product of the mass of the body and the acceleration due to gravity.
$\displaystyle \small \bullet$ Weight=mass × gravitational force
$\displaystyle \small W=mg$
$\displaystyle \small \bullet$ The weight of a body depends upon its location.
$\displaystyle \small \bullet$ Units of Weight:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg-m/sec^{2}$ or Newton
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm-cm/sec^{2}$ or Dyne
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb-ft/sec^{2}$ or Poundal
Density
$\displaystyle \small \bullet$ Mass per unit volume of a substance is called its density.
$\displaystyle \small Density=\frac{Mass}{Volume}$
$\displaystyle \small \bullet$ Units of Density:
$\displaystyle \small \circ$ M.K.S.: $\displaystyle \small kg/m^{3}$
$\displaystyle \small \circ$ C.G.S.: $\displaystyle \small gm/cm^{3}$
$\displaystyle \small \circ$ F.P.S.: $\displaystyle \small lb/ft^{3}$
m - mass of a body
g - acceleration due to gravity in $\displaystyle \small m/sec^{2}$ = 9.81 $\displaystyle \small m/sec^{2}$
V - volume of the body
ρ - density (pronounced as `rho')
W or FG - weight or weight force
Relative Density/Specific Gravity
$\displaystyle \small \bullet$ It is the ratio of the density of a given substance to the density of water at 4$\displaystyle \small ^{0}C$.
Methods to find Relative Density
1. Archimedes principle
$\displaystyle \small \bullet$ Weight of body when immersed in liquid=Total weight of body - Weight of liquid displaced by body
To find Relative density of solid insoluble in water
To find Relative density of liquid
To find Relative density of solid soluble in water
2. Using hydrometer
Nicholson Hydrometer: There is a hollow roller pin ‘A’ having hollow metallic cone ‘D’ joined at its bottom. The hydrometer is filled with wax or mercury to keep it balanced while floating in liquid. A thin rod ‘C’ is attached at the upper end of the roller pin. Point ‘B’, where the weights are to be placed.
To find Relative density of liquid
Laws of Floatation
$\displaystyle \small \bullet$ Assume,
$\displaystyle \small W_{1}$ = Weight of substance
$\displaystyle \small W_{2}$ = Weight of liquid displaced by substance
$\displaystyle \small \bullet$ If $\displaystyle \small W_{1}-W_{2}=0$, i.e. $\displaystyle \small W_{1}=W_{2}$ the weight of substance is equal to the upward thrust. Hence, the substance will float with difficulty.
$\displaystyle \small \bullet$ $\displaystyle \small W_{1}>W_{2}$ , the upward thrust is greater than the weight of the substance. Hence, the substance will rise in liquid till the weight of liquid displaced becomes equal to the weight of substance.
$\displaystyle \small \bullet$ If $\displaystyle \small W_{1}<W_{2}$ , the weight of the substance is greater than upward thrust. Hence, the substance will sink.
Specific Gravity of Substances
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