The substance used as moderator in nuclear reactor must MCQ with Answer and Explanation

Explanation:
According to Coulomb's Law, the electrostatic force (F) between two point charges is inversely proportional to the square of the distance (r) between them (F ∝ 1/r²). If the distance is doubled (r becomes 2r), the new force F' ∝ 1/(2r)² = 1/4r². Thus, the force becomes one-fourth of its original value.

Explanation:
v = u + at, linear relation, slope = a. Straight line inclined. If a=0, parallel to time axis (uniform velocity). Displacement-time is parabola for uniform acceleration.

Explanation:
Average speed = 2v₁v₂/(v₁+v₂) = 2×40×60/(40+60) = 4800/100 = 48 km/h. Not arithmetic mean (50). For equal distances, harmonic mean of speeds. If times equal, arithmetic mean applies.