General Science GK Questions with Answers – Page 118

Force has to be applied to break the chalk because its particles hold one another together, and that pull is the force of attraction between particles.

Constant velocity means no acceleration, and by Newton's second law force equals mass into acceleration, so the net force must be zero.

Platinum is the least reactive of the four, so it is found in nature in the free or native state as the metal itself.

Melting and boiling only have to break the weak forces between the molecules, not the strong bonds inside them, so little heat is needed.

By the work-energy theorem the work done equals the change in kinetic energy, which is half of 1.0 into 8 squared minus 4 squared, that is 0.5 × (64 - 16) = 24 joule.

Solder is an alloy of lead and tin, usually in nearly equal parts. An alloy is a mixture of a metal with one or more other elements, made to gain a property the pure metal lacks.

The zygote divides as it travels down the fallopian tube and the resulting ball of cells gets implanted in the thick lining of the uterus.

One kilowatt hour is 3.6 × 10⁶ joule, so 5.5 kWh = 5.5 × 3.6 × 10⁶ = 19.8 × 10⁶ joule.

Potential difference is defined as the work done for each unit of charge carried between two points, so V = W/Q and therefore W = QV.

Absolute pressure is counted from the absolute zero of pressure, which is a perfect vacuum, so it can never be negative.

Potential difference between two points of a circuit is the difference in electric potential between them, and it equals the work done in moving a unit positive charge from one point to the other.

A rise of 27°C is a rise of 27 K, because one degree Celsius and one kelvin are exactly the same size.

The mechanical energy of a body is the sum of the energy of its motion and the energy of its position.

A stretched bow stores elastic potential energy, and when the string is released that store becomes the kinetic energy of the flying arrow.

Work done against gravity is weight multiplied by height, so 120 × 2 = 240 joules.

Brakes work on friction: a lining is pressed against a moving drum or disc, and the rubbing force slows the wheel down.

Find each mass from F = ma, add the masses, then divide the same force by the total. The first block gives m1 = 5 ÷ 10 = 0.5 kg and the second gives m2 = 5 ÷ 20 = 0.25 kg.

Kinetic energy is half m v squared, so half of 22 multiplied by 5 multiplied by 5 gives 275 joules.

The body is thrown up at 20 m/s and gravity takes away 10 m/s of speed every second, so after 2 seconds its speed is zero.

Boron has three electrons in its outermost shell, so it is a trivalent element and is used as a p-type dopant.