General Science GK Questions with Answers – Page 106

Teflon is the trade name of polytetrafluoroethylene, a polymer whose surface is one of the most slippery among solids, with a coefficient of friction of about 0.04.

For the same pair of surfaces the order of friction is always static, then kinetic, then rolling. Static friction is the largest because the surfaces interlock while at rest and that grip has to be broken to start motion.

As the body falls its height shrinks, so the potential energy m g h falls, but exactly that much energy reappears as kinetic energy, half m v squared, because the body speeds up.

Fires are sorted into classes by what is burning, and a fire fed by flammable liquids such as petrol, diesel, kerosene, oil, paint or thinner is a class B fire.

The receptors that pick up taste are called gustatory receptors, and they sit inside the taste buds on the tongue.

In a class 3 lever the fulcrum is at one end, the effort is applied in the middle and the load sits at the far end.

Pitch is how shrill or how flat a sound seems to the ear, and it is decided by frequency, the number of vibrations per second measured in hertz.

The first equation of motion is written as v equals u plus a t, so it tells how the velocity of a body changes with time.

Water has a specific heat capacity of about 4186 joule per kilogram per kelvin, not 1200, so this pair is the wrong one.

A clinical thermometer is marked from 35 to 42 degrees Celsius, which on the Fahrenheit scale is 94 to 108 degrees.

A shortage of iodine makes the thyroid gland in the neck swell, a condition called goitre. The thyroid needs iodine to make the hormone thyroxine, and when iodine is short the gland grows larger to trap whatever little is available, so the neck looks visibly swollen.

A block lying quietly on a table is in equilibrium, so the forces on it must add up to zero, but that does not mean there are no forces at all.

An echo is the sound heard when a wave is reflected from a distant obstacle and comes back, so in the time measured the sound covers the distance to the cliff and then the same distance back again.

Plant tissues are first divided into meristematic tissue, whose cells keep dividing, and permanent tissue, whose cells have stopped dividing and have taken a fixed shape and job.

The middle ear holds three tiny bones, the smallest in the human body, called the malleus, the incus and the stapes, which in everyday English are the hammer, the anvil and the stirrup.

The force on a current-carrying conductor placed in a magnetic field is found with Fleming's left-hand rule.

Sound is a mechanical wave: it travels only when the particles of a medium push against their neighbours, so the closer and more tightly bound those particles are, the faster the disturbance is passed on.

Electrical energy is power multiplied by time, so the unit follows directly from the units you put in. The oven is rated 2500 W, which is 2500 divided by 1000, that is 2.5 kilowatts.

A unisexual flower carries only one kind of reproductive organ, either stamens or a pistil, while a bisexual flower carries both.

Power is the work done divided by the time taken, and here the work is the potential energy the boy gains while climbing the staircase.