General Science Mixed Quiz: Set 85

One pascal is defined as a force of one newton acting on an area of one square metre. Pressure is force per unit area, and its SI unit, named after the French scientist Blaise Pascal, is the pascal (Pa): 1 Pa = 1 N/m².

A beam seen from the side is visible only because tiny particles send some of its light sideways. Light travelling in a straight line cannot enter our eyes unless something redirects it towards us.

A healthy young human ear can hear sounds with frequencies from about 20 hertz to about 20,000 hertz. Frequency is the number of vibrations per second, measured in hertz, and our ears sense it as pitch.

Rotational kinetic energy is ½Iω², and the ring has the larger moment of inertia. For a thin ring about the axis through its centre and perpendicular to its plane, all the mass sits at distance R, so I = MR².

Field lines always leave a conductor normal to its surface, and for a positive charge they point away from it.

One parsec equals about 2,06,265 astronomical units, which rounds to 2 × 10⁵ A.U.

In ferric oxide both iron atoms are in the same +3 oxidation state. In Fe₂O₃ three oxide ions carry a total charge of −6, shared equally by two iron atoms, so each iron is +3.

An ion-exchange resin or zeolite swaps the calcium and magnesium ions that cause permanent hardness for sodium or hydrogen ions.

Methanoic acid, better known as formic acid, is the acid that ants inject when they sting, which is why the bite burns.

The anther is the top part of the stamen, the male organ of a flower, and pollen grains form inside it.

The liver cells (hepatocytes) are rich in smooth endoplasmic reticulum, whose enzymes break down drugs, alcohol and poisons into harmless forms.

On a level curve, friction alone supplies the centripetal force, so a cyclist slips when the needed force exceeds the maximum friction.

The pulmonary veins bring oxygen-rich blood from the lungs straight into the left atrium. The human heart has four chambers and works as two pumps.

If pressure is proportional to temperature for a fixed amount of ideal gas, the volume must stay constant, so the process is isochoric.

HIV spreads through body fluids such as blood, so a transfusion of infected blood passes the virus directly into the bloodstream.

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.

Guard cells are specialised epidermal cells that surround each stoma on the surface of a leaf. Each stoma is a tiny pore bordered by two guard cells, which are bean-shaped in most plants and dumb-bell shaped in grasses.

Chess skill is an acquired trait, built by learning and practice, and acquired traits are not passed on through genes.

The triple point is the single temperature and pressure at which the solid, liquid and vapour phases of a substance exist together in equilibrium.

Diagnostic laboratories spin blood samples in a centrifuge to separate the plasma or serum from the blood cells. In centrifugation a sample is rotated at high speed, so the denser particles are pushed to the bottom of the tube and the lighter liquid stays on top.