# Bouyant force

[SOLVED] Bouyant force

1. A ferry boat is 4.0 m wide and 6.0 m long. When a truck pulls onto it, the boat sinks 4.00 cm (0.04 m) in the water. What is the weight of the truck?

2. F(sub: B) = F(sub: g)[displaced fluid] = m(sub: f)g
(magnitude of bouyant force = weight of the fluid displaced)

F(sub: B) = F(sub: g)[object] = m(sub: o)g
bouyant force = weight of floating object

m = ρV
(mass = density × volume)

3. Well, the voulme of the boat is (4.0 m)(6.0 m)(0.04 m) = (0.96 m³); I mean, the volume of the displaced water is that. ;)

Density of fresh water = 1.00 × 10³ kg/m³

F = ρV(g)
F = (1.00 × 10³ kg/m³)(0.96 m³)(9.81 m/s²)
F = 9.4 × 10³ N

Am I correct?

Last edited:

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mgb_phys
Homework Helper
Correct - and an extra bonus point for quoting the weight of the truck not it's mass.
Although you will probably get the answer marked wrong by some dumb online marking system that expects mass.

All right! Thanks. :)

Problem solved!!!

EDIT: Ermmm... How do I mark it solved?

Found it. :)