or log in with
Submarines submerge and surface by changing the average density of the hull.
Due to their asymmetrical profile of the wings, lift is produced while flying at a high speed.
During freezing hydrogen bonds are formed between water molecules resulting in a crystal structure.
DC motors consist of a permanent magnet and a coil within the magnet, with electric current flowing in it.
In alkaline batteries electric current is generated by electrochemical reactions
The Earth's continents have been in constant motion during the history of the planet.
The length of the metal frameworks of bridges change when the temperature changes.
A fuel cell provides environment-friendly electric energy produced by the chemical reaction between oxygen and hydrogen.
Mercury is innermost and smallest planet of the Solar System.
A hot air balloon is a balloon aircraft which is lifted by hot air.
Electric current can be generated by rotating an armature loop in a magnetic field.
Neptune is the outermost planet of the Solar System, the smallest of the giant planets
Electrochemical processes in a lead-acid battery produce electric current.
The diameter of our galaxy is about 100,000 light years; it contains more than 100 billion stars, one of which is our Sun.
Venus is the 2nd planet from the Sun, the brightest object on the night sky (after the Moon).
A ray of light is reflected or refracted at the boundary of two mediums with different refractive indices.
Possible traces of water and life are sought on Mars.
A two-stroke engine is a type of internal combustion engine with a cycle of only two (power) strokes.
Cold and warm fronts are formed where bodies of cold and warm air meet.
Uranus is the 7th planet from the Sun, a gas giant.