The freezing point of mercury is -39°C. It cannot be used in thermometers for temperatures below this because MCQ with Answer and Explanation

Explanation:
R ∝ L/A ∝ 1/d². So R₁/R₂ = (d₂/d₁)² = (1/2)² = 1/4 = 1:4.

Explanation:
Volume of sphere V = (4/3)πr³. For error propagation, percentage error in V = 3 × (percentage error in r). Given error in r is 2%, so error in V = 3 × 2% = 6%. This follows the power rule: if Q = xⁿ, then % error in Q = |n| × % error in x. This principle is crucial for experimental error analysis. Exam tip: Remember that volume depends on cube of radius, so errors amplify threefold. This type of question tests understanding of error propagation in derived quantities.

Explanation:
54 km/h = 15 m/s. u=15, v=0, t=5. a = (0-15)/5 = -3 m/s². s = ut+½at² = 15×5 + ½×(-3)×25 = 75 - 37.5 = 37.5 m. Or s = (u+v)/2 × t = 7.5×5 = 37.5 m.