Sputnik I was launched into orbit around Earth in 1957. It had a perigee (the closest approach to Earth, measured from Earth's center) of 6.81 × 10⁶ m and an apogee (the furthest point from Earth's center) of 7.53 × 10⁶ m. What was its speed when it was at its perigee? The mass of Earth is 5.97 × 10²⁴ kg and
G = 6.67 x 10^-11 N•m²/kg².

Question

Quizplus · Accepted Answer

The speed at perigee can be calculated using the vis-viva equation: v = sqrt(GM(2/r - 1/a)), where r is the perigee distance, a is the semi-major axis, and GM is the gravitational parameter. The semi-major axis a = (perigee + apogee)/2. Plugging in the values, the speed at perigee is approximately 7.84 × 10^3 m/s.

Sputnik I Was Launched into Orbit Around Earth in 1957