Volume of a tetrahedron

To calculate the volume of a tetrahedron we start by calculating the volume of a prism.

Types of synovial joints

Synovial joints can be categorised by the direction of movement they allow.

Types of bridges

Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.


Oases are areas in deserts where water is available.

Fat molecule

Three saturated fatty acid molecules linked to a glycerol molecule.

Water turbine, generator

Water turbines convert the kinetic energy of water into electric current.

Mid-latitude cyclone and anticyclone

Cyclones are large areas of circulating air with clouds and precipitation being formed in its centre.

Warm front, cold front

Cold and warm fronts are formed where bodies of cold and warm air meet.

Underground waters

Groundwater and aquifers are types of underground waters.

El Niño

A periodic climate pattern that occurs across the tropical Pacific Ocean every five years.

Native American settlement (Crow Nation)

The Crow are Native Americans who inhabited the Yellowstone River valley.

Common carp

Freshwater fish used as food in many parts of the world.

Attack of Pearl Harbor (1941)

The United States entered World War II after the devastating attack by the Japanese navy.

Male reproductive system

The reproductive system consists of organs which work together for the purpose of reproduction.

Relief map of China

An introduction to the relief and hydrography of China.


The piano is one of the most popular instruments in the world. It is a chordophone which produces sounds mechanically.

Ancient Egyptian sailing boat

The river and marine sailing boats of ancient Egypt were one-masted, oared boats


This animation shows optical and radiotelescopes used in astronomical observation.

Horse chestnut

This animation demonstrates how horse chestnut trees change throughout the seasons


The most ancient group of animals, they live underwater, lack real tissues and body symmetry.

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