Which principle explains the working of hydraulic brakes? MCQ with Answer and Explanation

Explanation:
Average speed = Total distance / Total time. Let distance AB = d km. Time for AB = d/40 h, time for BA = d/60 h. Total distance = 2d km. Total time = d/40 + d/60 = d(3+2)/120 = 5d/120 = d/24 h. Average speed = 2d / (d/24) = 48 km/h. Note: Average speed is not arithmetic mean of speeds (which would be 50 km/h) because time intervals differ. This harmonic mean concept is crucial for motion problems. Exam tip: For equal distances, average speed = 2v₁v₂/(v₁+v₂). Frequently tested in competitive exams.

Explanation:
For closed pipe fundamental: L = v/(4f) = 340/(4×256) ≈ 340/1024 ≈ 0.332 m = 33 cm.

Explanation:
Hydrogen fusion to helium releases energy.