Average orbital speed from circumference and period

Steps:

• Convert period to seconds: T = 27 days × 24 h/day × 3600 s/h = 2.33 × 10^6 s.
• Calculate circumference: C = 2πr = 2 × 3.14 × 3.8 × 10^8 m = 2.39 × 10^9 m.
• Compute speed: v = C / T = 2.39 × 10^9 m / 2.33 × 10^6 s ≈ 1.0 × 10^3 m/s.
• Match to options: 1000 m/s.

Why A is correct:

• Orbital speed formula v = 2πr / T gives the average speed for circular orbit, matching 1000 m/s exactly.

Why the others are wrong:

• B underestimates by factor of 10, likely from miscalculating period or radius.
• C overestimates by ~40%, possibly from using incorrect π or day length.
• D overestimates by nearly 9x, perhaps confusing with linear speed or wrong units.

Final answer: A