Relief map of China

An introduction to the relief and hydrography of China.

Two-stroke engine

A two-stroke engine is a type of internal combustion engine with a cycle of only two (power) strokes.

Bells

The bell is a percussion instrument and an idiophone. Many types of bells exist.

Endocrine system

Glands of the endocrine system secrete hormones into the blood.

Gametes

The zygote is the initial cell formed when two gamete cells are joined by means of sexual reproduction.

Telescopes

This animation shows optical and radiotelescopes used in astronomical observation.

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.

Male reproductive system

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

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.

Types of gears

Two meshing gears transmit torque during their rotational motion.

Attack of Pearl Harbor (1941)

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

Dividing Space into Regions by 3 Planes

Division of space by three intersecting planes in several different arrangements.

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 surface epithelium

Surface epithelia cover the external and internal surfaces of the body

Types of bridges

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

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