Who is credited with the discovery of the electron? MCQ with Answer and Explanation

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:
In uniform circular motion, speed is constant but velocity direction changes continuously, requiring centripetal acceleration directed toward the center (a = v²/r). By Newton's second law, a centripetal force must act. Velocity isn't constant (direction changes); acceleration isn't zero; force is required. Memory tip: 'Uniform circular motion: constant speed, changing velocity, center-seeking acceleration'. This conceptual question tests understanding of circular dynamics, crucial for mechanics in competitive exams. Always distinguish speed (scalar) from velocity (vector) in motion analysis.

Explanation:
The distance covered in the nth second is Sn = u + a/2 * (2n - 1). For n=2: 12 = u + a/2 * (3) => 2u + 3a = 24. For n=4: 20 = u + a/2 * (7) => 2u + 7a = 40. Subtracting equations: 4a = 16 => a = 4 m/s^2. Substitute 'a' back: 2u + 3(4) = 24 => 2u = 12 => u = 6 m/s.