Multiple choice

An object travel $10\ km$ at a speed of $100\ m/s$ and another $10\ km$ at $50\ m/s$. The average speed over the whole distance is

  1. $75\ m/s$
  2. $55\ m/s$
  3. $66.7\ m/s$
  4. $33.3\ m/s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Average speed = Total distance / Total time. Distance 1 = 10 km = 10000 m. Time 1 = 10000 / 100 = 100 s. Distance 2 = 10000 m. Time 2 = 10000 / 50 = 200 s. Total distance = 20000 m. Total time = 300 s. Average speed = 20000 / 300 = 66.7 m/s.

AI explanation

Since the two equal distances are traveled at different speeds, apply the average speed formula 2xy / (x + y). Substituting the given values gives (2 * 100 * 50) / (100 + 50), which simplifies to 10000 / 150. The average speed over the whole distance is 66.7 m/s.

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