An iron sphere of mass 10 kg has same diameter as an aluminium sphere of mass 3.5 kg. Both fall from rest in vacuum. Which hits ground first? MCQ with Answer and Explanation

Explanation:
Using v² = u² - 2gH, at maximum height v = 0. So 0 = 20² - 2×10×H => 400 = 20H => H = 20 m. Alternative formula: H = u²/(2g) = 400/20 = 20 m. Remember to use consistent units. For quick calculation, u²/(2g) is handy.

Explanation:
Coulomb is the SI unit of electric charge, but it is a derived unit (Ampere × second). The seven fundamental SI units are meter (length), kilogram (mass), second (time), Kelvin (temperature), Ampere (electric current), candela (luminous intensity), and mole (amount of substance). Electric current is fundamental, making Ampere fundamental, not Coulomb.

Explanation:
Concave lens diverges light, always forms virtual, erect, diminished image on same side as object. Used in spectacles for myopia.