Two resistance wires of same material and same length have diameters in ratio 2:1. Their resistances are in ratio MCQ with Answer and Explanation

Explanation:
Newton's First Law states that a body at rest stays at rest, and a body in motion stays in uniform motion unless acted upon by an external unbalanced force. This inherent property of matter to resist any change in its state of rest or motion is called inertia, hence it is known as the Law of Inertia.

Explanation:
Newton's second law: F = ma ⇒ a = F/m = 20 N / 5 kg = 4 m/s². Direct application of fundamental dynamics equation. Memory tip: Always convert to SI units first; here already in kg and N. Basic numerical testing F=ma application, commonly appearing in competitive exams to verify formula recall and unit handling.

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.