General Science Previous Year Questions (PYQ) with Answers – Page 85

A microwave oven does not cook by passing a current through a resistance. It generates microwaves in a magnetron, and these waves make the water molecules in the food rotate rapidly, so the food heats from within by dielectric heating.

The work done against gravity is mgh = 40 × 10 × 5 = 2000 joule, and power is work divided by time, so 2000 ÷ 4 = 500 watt.

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.

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.

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.

At normal atmospheric pressure water stays liquid between 0 °C and 100 °C, and 12 °C lies inside that range.

Kinetic energy depends on the square of the momentum, so the momentum grows as the square root of the energy.

The stamen and the pistil make the male and female gametes, so they are the essential or reproductive organs of a flower.

Silver is a noble metal and does not combine with oxygen even when it is heated strongly. Metals react with oxygen according to their place in the reactivity series.