1)An alloy of copper zinc has a mass of 4.9kg.when suspended in water.0.98kg of water was displaced by it.calculate the mass of zinc in the alloy if 2.5 and 19.6 are the specific gravity of the zinc and copper respectively

Question

2) A steel ball of diameter 0.2mm, falls with a terminal velocity of 0.0029m/s through oil in a relatively large jar.Calculate the viscosity of oil, assuming the densities of the oil and the ball ar to be 7200 and 420kg/m^3 respectively .if the radius is doubled,calculate the new terminal velocity.[take g=9.8m/s^2]

Answer 1

.98 kg of water is .98 *10^-3 m^3 of volume

mass of zinc = z
mass of copper = (4.9-z)
volume of zinc = z * 2.5*10^-3 m^3
volume of copper = (4.9-z)* 19.6*10^-3 m^3

so
z*2.5*10^-3+(4.9-z)*19.6*10^-3 =.98*10^-3