A new unit α of length is defined in the question such that one α corresponds numerically to 3×10⁸ m. Light takes 6 min 40 s to travel from Venus to Earth. What is this distance in α units?
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Question

A new unit α of length is defined in the question such that one α corresponds numerically to 3×10⁸ m. Light takes 6 min 40 s to travel from Venus to Earth. What is this distance in α units?

G1 Physics · Accepted Answer

The given travel time is t = 6 min 40 s = 6×60+40 = 400 s. The speed of light is c = 3×10⁸ m·s⁻¹. Therefore the distance is d = ct = 3×10⁸×400 = 400×3×10⁸ m. By the unit definition used in the question, 1 α = 3×10⁸ m. Hence, d = 400 α. Correct option: B.