A ball is thrown upward with velocity 30 m/s. Time to reach maximum height (g=10) is MCQ with Answer and Explanation

Explanation:
Superconductivity occurs in certain materials below a critical temperature T_c, where electrical resistance drops abruptly to zero, and magnetic fields are expelled (Meissner effect). Option B describes insulators; C and D are unrelated. Memory aid: 'Superconductor: R=0 below T_c; perfect diamagnetism'. This modern physics concept is frequently tested in competitive exams. Always distinguish superconductivity (zero resistance) from perfect conductivity (theoretical limit); real superconductors exhibit Meissner effect, a defining property.

Explanation:
Beat frequency = |260 - 256| = 4 Hz ⇒ 4 beats/second. Interference of close frequencies causes amplitude modulation. Memory aid: 'Beats = frequency difference; used in tuning instruments'. Wave interference calculation frequently tested in competitive exams.

Explanation:
ΔU = GMm (1/R - 1/(R+2R)) = GMm (1/R - 1/3R) = (2/3)GMm/R = (2/3)mgR.