Astrophysics

6 marks · Normal

A newly launched artificial satellite is put into a circular orbit 2000 km above Earth's surface. Its time period for one complete orbit is 2 hours. The mass of the satellite is 1000 kg. The next night, you observe Jupiter through a telescope and identify several of its natural satellites (moons).

(a)

Calculate the orbital speed of the satellite. Give your answer in m/s.

(b)

State the SI unit used for mass in astrophysics, and explain whether the mass of the satellite affects its orbital speed.

[2 marks]

(c)

State one similarity and one difference between the orbits of moons and artificial satellites around Jupiter.

[1 mark]

(b)

State the SI unit used for mass in astrophysics, and explain whether the mass of the satellite affects its orbital speed.

[2 marks]

(c)

State one similarity and one difference between the orbits of moons and artificial satellites around Jupiter.

[1 mark]

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) orbital speed , where Earth's radius + altitude = 6,371,000 + 2,000,000 = 8,371,000 m, hours = 7200 s, so m/s

(b) The SI unit of mass is kilogram (kg). The mass of the satellite does not affect its orbital speed for a given orbit around Earth.

(c) Similarity: Both are held in orbit by gravity. Difference: Moons are natural, satellites are artificial (human-made).

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Correctly substitutes orbital radius and time into the formula.

A1 (a) · 1 mark · Correctly converts units and calculates circumference or period. (follow-through)

A1 (a) · 1 mark · Calculates correct speed to within the tolerance given. (follow-through)

B1 (b) · 1 mark · States kilogram (kg) as the SI unit for mass.

M1 (b) · 1 mark · Explains mass does not affect orbital speed in a given orbit.

B1 (c) · 1 mark · States one similarity and one difference between moons and artificial satellites.

Worked solution

a) The orbital speed is . Earth's radius m, so total radius m. Time period hours s.

b) The SI unit of mass is kilogram (kg). The mass does not affect orbital speed, because all objects at the same orbital radius and period travel at the same speed, regardless of their mass.

c) Similarity: Both are held in orbit by gravity. Difference: Moons are natural; satellites are artificial and placed in orbit by humans.