Mirror focal length f and radius R relation: MCQ with Answer and Explanation

Explanation:
T = 2π√(m/k). Depends on mass and stiffness.

Explanation:
Though the ship is made of iron, it is hollow inside and traps a large volume of air. This makes the overall or average density of the ship less than the density of water. According to the law of floatation, an object floats if its average density is less than that of the fluid. A solid iron needle has a higher density than water, so it sinks.

Explanation:
When B starts, A has already traveled 10 m/s × 2 s = 20 m. Relative velocity of B w.r.t A = 15 - 10 = 5 m/s. Time to cover 20 m gap at 5 m/s relative speed = 20/5 = 4 s after B starts. Since B started 2 s late, total time from A's start = 2 + 4 = 6 s. Alternatively, equate distances: 10t = 15(t-2) ⇒ 10t = 15t - 30 ⇒ t = 6 s. This relative motion approach simplifies pursuit problems. Memory tip: In same-direction motion, use relative velocity = |v₁ - v₂|. Frequently tested in kinematics sections of competitive exams.