Units (Astrophysics)
2 marks · NormalA student says a planet's mass is '6000 kg'. What is wrong with this answer in the context of planetary science? Explain your answer.
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6000 kg is a much too small value for the mass of a planet. Planets have masses many orders of magnitude greater, usually expressed in kilograms with a multiplier (e.g., 6 × 10^24 kg for Earth).
Also accept: Planets are much more massive than 6000 kg; typical planets have masses of about 10^24 kg or more.
Common mistakes: Failing to mention the scale of planetary masses.
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Marking points
B1 · 1 mark · Recognises that 6000 kg is too small for a planet.
B2 · 1 mark · Mentions typical planet masses are much higher, e.g., 10^24 kg, or gives comparison (Earth's mass).
Worked solution
6000 kg is far too small for a planet’s mass—in reality, planets have masses of 10^24 kg or greater, for example the Earth’s mass is roughly 6 × 10^24 kg.