Question

A beaker of mass 5kg containing oil of mass 17.4 kg and density 8.5 x102kg/m3 rests on the scale

A block of iron of mass 6.7kg is suspended from the spring scale and completely submerged in the oil as shown in Figure below. Determine the equilibrium readings of lower scale in newtons. ( iron density is 7200 kg/m3).

Answer 1

ok, the first thing to do is figure the bouyant force on the iron.

forceB=density*volume*g
= volume iron*density oil*g
= massiron/density iron * density oil*g

so the upper sting is holding the weight of iron, less bouyant force or
upper=6.7*g-forceB

and the lower force is the weight of the beaker, oil, and bouyant force on the iron.

lowerforce=5*g + 17.4*g + force B

were g= 9.8N/kg