Question

A rock weighs 140 N in air and has a volume of 0.00273 m3. What is its apparent weight when sub-
merged in water? The acceleration of gravity is 9.8 m/s2 . Answer in units of N.
If it is submerged in a liquid with a density exactly 1.9 times that of water, what will be its new apparent weight?
Answer in units of N.

Answer 1

apparent weight= true weight-bouyancy
= 140N- weight of water displaced
= 140N- densitywater*g*volume

Answer 2

but..how do i get the weight of water displaced? i don't get that part. because if i do
140- (.00273*9.8*5232.86) =0

Answer 3

The weight of water displaced is
density of fluid * g * volume of fluid displaced
the density of water is about 1000 kg/m^3

so buoyant force up in water =
1000 * 9.8 * .00273
= 26.75 Newtons
so in water it will weigh
140 - 26.75 = 113 N

Answer 4

for the second part use 1900 kg/m^3 for the density of the fluid