Practice Buoyancy in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Worksheet PDF Free Answer-key PDF Family

Quick Recap

Buoyancy is the upward force a fluid exerts on an object that is partly or fully immersed in it.

Water pushes up more on the bottom of an object than on the top, so the object feels an upward lift.

Showing a random 20 of 50 problems.

Example 1

easy
A diver pushes a fully submerged ball that displaces 0.005 m30.005 \text{ m}^3 of water (ρ=1000\rho=1000, g=10g=10). Find the buoyant force.

Example 2

hard
A block of density 400 kg/m3400 \text{ kg/m}^3 and volume 0.001 m30.001 \text{ m}^3 is held under water by a string from below (ρ=1000\rho=1000, g=10g=10). Find the tension in the string.

Example 3

easy
A boat floats. Compared to its weight, the buoyant force is: greater, less, or equal?

Example 4

easy
Archimedes' principle says the buoyant force on an object equals the weight of the ___ it displaces.

Example 5

hard
A 0.3 kg0.3 \text{ kg} ball of volume 0.0004 m30.0004 \text{ m}^3 is released from rest underwater (ρ=1000\rho=1000, g=10g=10). Find its initial acceleration (ignore drag).

Example 6

challenge
A hydrometer of mass 0.02 kg0.02 \text{ kg} and uniform cross-section 0.0001 m20.0001 \text{ m}^2 floats in a liquid. It sinks to a depth of 0.25 m0.25 \text{ m}. Find the liquid's density. (g=10g=10)

Example 7

easy
An object weighs 50 N50 \text{ N} in air and 30 N30 \text{ N} when submerged. Find the buoyant force.

Example 8

medium
An iceberg (ρ=920\rho=920) floats in seawater (ρ=1025\rho=1025). What fraction is below the surface?

Example 9

easy
An object of volume 0.003 m30.003 \text{ m}^3 is half submerged in water (ρ=1000\rho=1000, g=10g=10). Find the buoyant force.

Example 10

easy
A buoyant force of 25 N25 \text{ N} acts on a fully submerged object in water (ρ=1000\rho=1000, g=10g=10). What volume does it occupy?

Example 11

easy
A helium balloon of volume 0.5 m30.5 \text{ m}^3 sits in air (ρ=1.2\rho=1.2, g=10g=10). Find the buoyant force air exerts on it.

Example 12

medium
A 3 kg3 \text{ kg} rock of volume 0.001 m30.001 \text{ m}^3 is lowered into water (ρ=1000\rho=1000, g=10g=10) by a rope. Find the tension in the rope when the rock is fully submerged and at rest.

Example 13

easy
The buoyant force on a floating log equals its weight of 300 N300 \text{ N}. What is the buoyant force?

Example 14

easy
An object displaces 0.002 m30.002 \text{ m}^3 of water (ρ=1000\rho=1000, g=10g=10). Find the buoyant force.

Example 15

easy
A cube displaces 0.0008 m30.0008 \text{ m}^3 of seawater (ρ=1025\rho=1025, g=10g=10). Find the buoyant force.

Example 16

challenge
A cube of side 0.1 m0.1 \text{ m} floats at the interface of oil (ρ=800\rho=800) on top and water (ρ=1000\rho=1000) below. Half its volume is in each. Find the cube's density. (g=10g=10)

Example 17

challenge
A balloon of volume VV filled with helium (ρHe=0.18\rho_{He}=0.18) sits in air (ρair=1.2\rho_{\text{air}}=1.2, g=10g=10). The envelope weighs 5 N5 \text{ N}. Find the minimum VV so the balloon just lifts off (zero payload).

Example 18

hard
A 5 kg5 \text{ kg} rock of volume 0.002 m30.002 \text{ m}^3 sits on the bottom of a tank of water (ρ=1000\rho=1000, g=10g=10). Find the normal force from the tank floor.

Example 19

challenge
A 1 kg1 \text{ kg} object of volume 0.0005 m30.0005 \text{ m}^3 rests on the bottom of a tank. Find the normal force from the floor when submerged in water. (ρ=1000\rho=1000, g=10g=10)

Example 20

challenge
A block of density 900 kg/m3900 \text{ kg/m}^3 sits at the interface of oil (ρ=800\rho=800) on top and water (ρ=1000\rho=1000) below, with part in each. What fraction of its volume is in the water?
← Back to Buoyancy Worked Examples Formula Explained