Q4 · 2024 · Paper 2Simple familiar4 marks
QUESTION 4 (4 marks)
Explain how a satellite can be accelerating yet maintain a constant speed in a circular orbit around a planet.
WORKED SOLUTION
4 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
The satellite has inertia and, in the absence of the
planet, would continue in a straight line with the
same speed until acted upon by an unbalanced
force.
When the planet’s gravitational force pulls the
satellite towards it (perpendicular to the satellite’s
motion), the satellite changes direction and thus
accelerates towards the planet, but its speed does
not change.
As a result, the satellite continues to move
‘forward’, but the planet’s gravitational force pulls
the satellite towards it. So the resultant motion is
that the satellite has a constant speed (not velocity
as direction is changing) travelling in a circle
around the planet.
• describes inertia of satellite [1 mark]
• identifies that planet provides a centripetal
force [1 mark]
• identifies that the centripetal force is
perpendicular to the satellites motion
[1 mark]
• explains that changing direction means
change in velocity which is acceleration
[1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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