This animation demonstrates how solar energy can be utilised.
An introduction to the relief and hydrography of China.
A two-stroke engine is a type of internal combustion engine with a cycle of only two (power) strokes.
The bell is a percussion instrument and an idiophone. Many types of bells exist.
Glands of the endocrine system secrete hormones into the blood.
The zygote is the initial cell formed when two gamete cells are joined by means of sexual reproduction.
This animation shows optical and radiotelescopes used in astronomical observation.
Cyclones are large areas of circulating air with clouds and precipitation being formed in its centre.
Cold and warm fronts are formed where bodies of cold and warm air meet.
The reproductive system consists of organs which work together for the purpose of reproduction.
Groundwater and aquifers are types of underground waters.
A periodic climate pattern that occurs across the tropical Pacific Ocean every five years.
The Crow are Native Americans who inhabited the Yellowstone River valley.
Two meshing gears transmit torque during their rotational motion.
The United States entered World War II after the devastating attack by the Japanese navy.
Division of space by three intersecting planes in several different arrangements.
To calculate the volume of a tetrahedron we start by calculating the volume of a prism.
Synovial joints can be categorised by the direction of movement they allow.
Surface epithelia cover the external and internal surfaces of the body
Types of bridges include beam-, arch-, suspension-, cantilever and truss bridges.