General Science Mixed Quiz: Set 28

The law of conservation of linear momentum follows straight from Newton's second law: the rate of change of the momentum of a system equals the net external force acting on it, so when that force is zero the total momentum stays the same in size and in direction.

A ligament is the connective tissue that joins one bone to another at a joint. It is very elastic and strong, and it holds the bones in place so that a joint can move without the bones slipping apart.

The force on a current carrying conductor kept in a magnetic field is given by F equal to B I L sin theta, where theta is the angle between the direction of the current and the direction of the field.

The BCG vaccine takes its name from Albert Calmette and Camille Guerin, the two French scientists who developed it from a weakened strain of Mycobacterium bovis.

Johann Wolfgang Dobereiner, a German chemist, grouped elements of similar properties in sets of three that he called triads. His rule was that the atomic mass of the middle element is about the average of the other two.

Bacteria are grouped by shape, and bacilli are the rod-shaped ones; the Latin word bacillus itself means a small rod or stick.

Ethylene, also called ethene, has the formula C2H4, and its two carbon atoms share two pairs of electrons, which is a carbon-carbon double bond made of one sigma and one pi bond; it is the simplest alkene.

In a suspension the particles of the solute are large enough to be seen and do not dissolve; they stay spread through the liquid only while it is stirred and settle to the bottom when it is left standing.

The pH is the negative logarithm of the hydrogen ion concentration, so each rise of one unit means the concentration has fallen to one tenth.

Calaverite is gold telluride, with the formula AuTe2. It is one of the very few minerals in which gold occurs chemically combined rather than as the free metal, because gold is a noble metal that usually resists reaction.

A wet chemical extinguisher sprays a fine mist of a potassium salt solution — usually potassium acetate, potassium citrate or potassium carbonate — so potassium is the working element inside it.

Among the four, the ant has the largest brain in proportion to its body. An ant’s brain is tiny in absolute terms, with about two hundred and fifty thousand neurons, yet it makes up roughly a sixth of the insect’s body weight, a share no vertebrate comes close to.

Bacteria are prokaryotes, so their DNA lies free in the cytoplasm instead of being packed inside a nucleus. The single circular chromosome sits in a region of the cytoplasm called the nucleoid, which has no nuclear membrane around it.

A normal umbilical cord contains two arteries and one vein, three blood vessels in all. The umbilical cord joins the developing foetus to the placenta.

The alveoli are the tiny balloon-like air sacs at the ends of the smallest airways, and their thin walls are the surface where gases are exchanged.

Abscisic acid is the one plant hormone in this list that slows growth instead of speeding it up, which is why it is often called the stress hormone of plants.

The pulmonary artery is the one artery in the body that carries deoxygenated blood. It leaves the right ventricle and takes blood that has returned from the body's tissues to the lungs, where carbon dioxide is given up and fresh oxygen is picked up.

Adrenaline, also called epinephrine, is made by the medulla of the adrenal gland and is the body's emergency hormone; it makes the heart beat faster and stronger and narrows the small blood vessels, so blood pressure rises within seconds.

The carbohydrates in our food are broken down into glucose, and the glucose that the body does not need at once is stored as glycogen, a branched chain of glucose units kept mainly in the liver and the skeletal muscles.

Green plants give out oxygen only during photosynthesis, the process in which they use light energy to make their own food.