Answer: A) less than Explanation: This orbital velocity at the moon is less because orbital velocity = rg   where 'r ' is the orbital radius. i.e the distance of the body from the center of the earth and 'g' is the acceleration due to gravity on the body in question. In the case of the moon, both r and g are less than in the case of the earth.

Answer: C) strong opposite charges in different clouds break down the resistance offered by the intervening air Explanation: When the resistance of the air between breaks down the current flows from the positive cloud to the negative cloud in a flash which we call lightning . The difference of potential involves is very high.

Answer: D) falling of ultra violet rays on the white inner coating of the tube Explanation: The ultraviolet rays have high frequency and shorter wavelength are converted to visible white light with lower frequency and greater wave length

Answer: D) it is ready to produce controlled energy Explanation: To produce controlled energy i.e energy at a controlled or steady rate, the number of fissions per second must be controlled and maintained at that rate. Excess neutrons should be absorbed by control roads like cadmium.

Answer: B) sodium carbonate Explanation: Sodium hydroxide - NaOH is caustic soda   Sodium carbonate - Na2CO3 is washing soda   Sodium bicarbonate - NaHCO3  is baking soda

Answer: D) atomic number Explanation: Atomic number is the serial number of an element in the periodic classification of elements. It gives the number of protons and also the number of electrons in an atom.

Answer: D) Sulphuric acid Explanation: Sulphuric acid is called the King of Chemicals because it is used in the preparation of a very large number of other useful chemicals such as hydrochloric acid, nitric acid, dyes, drugs etc. In fact the annual production of shulpuric acid in a country is a measure of the economy of the country.

Answer: D) white phosphorus Explanation: White phosphorus undergoes spontaneous combustion when exposed to air. In order to prevent this spontaneous ignition, it is preserved under water.