Challenging Physics Problem?

Question

Devi places a jar with a penny inside into a pool of water. The volume of the jar is 200cm^3. Exactly half of the jar is submerged below the surface.

a.) What is the buoyant force acting on the jar?

b.) What is the mass of the jar?

Answer 1

a.) Buoyant force:

B = ρ(water)*g*V

V will be half of the given volume, as only half of the jar is submerged.  Convert cm³ to m³ using conversion factor of (1m)³/(100cm)³.

ρ(water) is the density of water (~1000kg/m³).

b.) Plug in B to find mass:

B = mg  -->  m = B/g

The buoyant force equals the force of gravity, hence the jar floats.