The part of human eye that controls amount of light entering is MCQ with Answer and Explanation

Explanation:
For equal distances: average speed = total distance/total time = 2d/(d/v₁ + d/v₂) = 2v₁v₂/(v₁+v₂). This is harmonic mean, not arithmetic. Memory tip: Equal distances ⇒ harmonic mean of speeds; equal times ⇒ arithmetic mean. Frequently tested kinematics concept distinguishing average speed calculation methods.

Explanation:
Time of flight T = 2u/g = 2×49/9.8 = 98/9.8 = 10 s. Up and down symmetric. Max height = u²/(2g) = 122.5 m.

Explanation:
Hydrogen fusion to helium releases energy.