General Science Mixed Quiz: Set 71

A light year is a unit of distance, not of time or brightness. One light year is the distance light travels through a vacuum in one Julian year.

Accelerators speed up the vulcanisation of rubber; they are not a part of paint.

Two equal forces give a resultant of the same size only when they are 120° apart, and the resultant then makes 60° with each.

In a class 3 lever the effort is applied between the fulcrum and the load, so the effort always sits nearer the fulcrum and its arm is the shorter of the two.

All the potential energy at the top turns into kinetic energy at the mean position, so v = √(2gh) = √(2 × 10 × 0.20) = 2 m/s. When the bob is released from rest at height h, it has potential energy mgh and no kinetic energy.

The pinna is the outer, visible flap of the ear, and its funnel shape collects sound from the surroundings. Sound gathered by the pinna travels down the ear canal to the tympanic membrane, or eardrum, which starts to vibrate.

Gravitational force varies inversely as the square of the distance, so halving the distance makes the force 2 × 2 = 4 times larger.

The petiole is the stalk that joins a leaf blade to the stem; it belongs to the leaf, not to the flower, and a leaf without one is called sessile.

Using Q = mcΔT, the mass works out to 20,000 ÷ (400 × 10) = 5 kg. The heat needed to warm a body is Q = mcΔT, where m is the mass, c the specific heat capacity and ΔT the rise in temperature.

Coulomb friction, also called dry friction, is the resistance that acts when two solid surfaces touch each other with no lubricant between them.

A mirage forms when light from the sky bends through hot, less dense air near the ground and is finally totally internally reflected.

Charles’s law says that at constant pressure the volume of a fixed mass of gas is directly proportional to its absolute temperature, so V by T stays constant.

A body moving faster than sound outruns its own sound waves, which pile up into a shock wave heard on the ground as a sonic boom.

Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there.

Silver is the best conductor, nichrome is an alloy with high resistivity, and glass is an insulator with enormous resistivity.

The balanced equation for the complete combustion of glucose is C6H12O6 plus 6O2 gives 6CO2 plus 6H2O, so one mole of glucose needs six moles of oxygen gas.

Of the four options, oxygen is by far the most plentiful element; it makes up about 46% of the Earth's crust by mass.

Copper in the +1 state is reduced to metal, so it is the oxidant; sulphur of Cu2S is oxidised, so it is the reductant.

A carbonate reacts with an acid at room temperature to give carbon dioxide, and only carbon dioxide turns limewater milky.

Copper is less reactive than lead, so it cannot push lead out of its compound. In a displacement reaction, a more reactive metal takes the place of a less reactive metal in its salt solution.