Lesson: Buoyant Force Physics • 9th Grade
In this lesson, we will learn how to compare an object’s weight to the weight of the fluid displaced by an object, and explain how this determines an object’s buoyancy.
A submarine under the sea has a lower density than the seawater around it, which is 1,025 kg/m3, because most of the submarine’s volume consists of air that has a density of 1.225 kg/m3. If of the submarine’s volume is air and of its volume is steel of density 7,700 kg/m3, how many times greater is the upthrust force that the water applies to the submarine than the submarine’s weight? Round your answer to one decimal place.
A cube-shaped object, with sides that are 130 cm long each, has a density of 950 kg/m3. The cube is placed into a body of water. The water has a density of 1,000 kg/m3.
What is the volume of the object in cubic meters?
What is the mass of the object? Answer to the nearest kilogram.
How many cubic meters of water have a mass equal to that of the object?
How far below the water’s surface must the base of the object be in order to displace a mass of water equal to that of the object? Answer to the nearest centimeter.
A cuboid-shaped object floats at rest in water of density 1,000 kg/m3. The top of the object is at a depth of 2.5 m and its base is at a depth of 5.5 m.
How much greater is the pressure exerted by water at the object’s base than at its top?
The horizontal faces of the object both have an area of 0.25 m2. How much greater is the force exerted by water at the object’s base than at its top?