The escape velocity for a projectile on the Earth's surface is 11.2 km/s. If a body is projected at twice this velocity, what happens? MCQ with Answer and Explanation

Explanation:
Power P = 1/f (in meters). P = -2 D ⇒ f = 1/(-2) = -0.5 m = -50 cm. Negative focal length indicates diverging (concave) lens. Convex lenses have positive power. Option A correctly states concave lens with |f| = 50 cm. Memory tip: 'Negative power = concave lens; f(in cm) = 100/P(in D)'. This direct application of lens power definition is common in competitive exams. Always convert diopters to focal length carefully, noting sign convention: negative for diverging lenses, positive for converging.

Explanation:
Resistance depends on the resistivity of the material (R = ρL/A). Silver and copper are excellent conductors with very low resistivity. Aluminum is also a good conductor. Nichrome is an alloy (nickel, chromium, and often iron) with a resistivity about 60 times higher than that of copper, making it a resistor used in heating elements.

Explanation:
g = 4π²l/T² ⇒ %Δg = %Δl + 2×%ΔT. Assuming l precise: %Δg ≈ 2×(0.1/2.0×100%) = 2×5% = 10%. Memory tip: 'g ∝ 1/T² ⇒ %Δg = 2×%ΔT'. Error analysis frequently tested in competitive experimental physics sections.