Liquids in a U-tube, Archimedes’ force and floating
Answers are for parents and teachers.
1
h_water = 16 cm, h_oil = 20 cm. Find the oil density (kg/m³).
800
2
What is the buoyant force on a fully submerged 7-litre body in N? (g ≈ 10 N/kg)
70
3
What percent of wood of density 500 kg/m³ is submerged in water?
50
4
At home: observe a boiled egg sink in a glass of water and note when it floats as salt is added. Write the result.
As salt is added the water’s density rises; with enough salt the egg floats.
5
Why is overloading a ship dangerous? Explain with the waterline.
More cargo makes the ship sit deeper; beyond the waterline mark water can get in and the risk of sinking grows.