General Science Mixed Quiz: Set 12

The third law says that to every action there is an equal and opposite reaction, and the crucial point is that the two forces act on two different bodies.

It states that the upthrust on a body dipped fully or partly in a fluid equals the weight of the fluid the body pushes aside.

A dynamo, also called a generator, is turned by some mechanical agency such as falling water, steam or a bicycle wheel, and the rotation of a coil in a magnetic field produces an electric current by electromagnetic induction.

LIGO, the Laser Interferometer Gravitational-Wave Observatory in the USA, detected gravitational waves for the first time in September 2015 (announced in February 2016), and such waves were predicted by Einstein's general theory of relativity in 1916.

The slope of any graph is the change on the vertical axis divided by the change on the horizontal axis; here that is distance divided by time, which is speed by definition.

The stapedius, only about 1 millimetre long, is the smallest skeletal muscle in the human body. It lies in the middle ear and is attached to the stapes, which is itself the smallest bone of the body.

The work-energy theorem states that the net work done on a body equals the difference between its final and initial kinetic energies, which is why a push that speeds a body up does positive work while friction, which slows it, does negative work.

Work equals force into displacement into the cosine of the angle between them, and the cosine of ninety degrees is zero, so a force at right angles to the motion does no work at all.

Inertia is the tendency of a body to resist any change in its state of rest or of uniform motion, and the heavier the body the harder it is to start or to stop.

At great heights the air is thin, so the atmospheric pressure acting on the body is much lower than at sea level.

The force he applies to support the load acts vertically upward, while his displacement along the platform is horizontal, so the angle between force and displacement is ninety degrees and the work done against gravity is zero, however tired he may feel.

Water is densest at about 4 degrees Celsius, and 4 plus 273 gives roughly 277 kelvin. Most liquids keep shrinking as they cool, but water behaves oddly: below 4 degrees Celsius it starts to expand again because its molecules begin forming the open, hexagonal pattern of ice.

Whether the hands are moved or not, the momentum of the ball must be brought down to zero.

A healthy human ear can hear sound waves with frequencies from about 20 hertz to 20,000 hertz (20 kHz); this band is called the audible range.

A stone at rest at a height has no motion and therefore no kinetic energy, but it possesses gravitational potential energy equal to its mass into the acceleration due to gravity into the height of the tower.

Water is called the universal solvent because its molecule is polar: the oxygen end carries a partial negative charge and the two hydrogen ends carry partial positive charges.

The erg is the unit of work in the CGS system, being one dyne of force acting through one centimetre, and since one newton is one lakh dyne and one metre is a hundred centimetre, one joule works out to ten million erg, that is 10 raised to the power…

Washing soda is sodium carbonate decahydrate: each unit of sodium carbonate holds ten molecules of water of crystallisation. It is made from common salt in steps: baking soda is heated to get anhydrous sodium carbonate, called soda ash, which is then recrystallised from water to give washing soda crystals.

At the top the object holds only potential energy; as it falls, that store is steadily converted into kinetic energy, and just as it touches the ground almost all of it is kinetic.

Galvanisation is the coating of iron or steel with a thin layer of zinc so that the iron underneath does not rust.