Astrophysics
4 marks · EasyA satellite travels in a circular orbit around Earth. The radius of its orbit is 7,000 km and it takes 2 hours to complete one orbit.
Calculate the circumference of the orbit. Give your answer in km.
Calculate the orbital speed of the satellite in km/h. Use: speed = distance/time.
What is the correct SI unit for speed? (Give the symbol.)
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) circumference = 2 × π × radius = 2 × 3.14 × 7000 = 43,960 km (accept 44,000 km) km
(b) speed = distance/time = 43,960 / 2 = 21,980 km/h
(c) m/s
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correct formula and substitution for circumference
M1 (b) · 1 mark · Speed calculated using c/t
A1 (b) · 1 mark · Correct final value for speed
B1 (c) · 1 mark · Correct SI unit (m/s)
Worked solution
a) Circumference = 2 × π × 7000 = 2 × 3.14 × 7000 = 43,960 km
b) Orbital speed = 43,960 km / 2 h = 21,980 km/h
c) The SI unit for speed is m/s