Satellites and moons
3 marks · NormalThe planet Jupiter has many moons orbiting it. One of these moons, Europa, follows a nearly circular orbit due to the gravitational attraction from Jupiter.
State what provides the force needed to keep Europa moving in its orbit around Jupiter.
Explain why Europa does not fly off into space.
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(a) Gravitational attraction (between Jupiter and Europa)
(b) Gravity acts towards Jupiter, providing the centripetal force that keeps Europa in a curved path instead of moving off in a straight line. · must show Reference to centripetal force OR curved path
Common mistakes: Saying inertia keeps moon in orbit
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Marking points
B1 (a) · 1 mark · States gravity (gravitational attraction) as the force keeping Europa in orbit.
B2 (b) · 1 mark · Explains gravity acts towards Jupiter (centre of orbit) and does not act tangentially.
B3 (b) · 1 mark · Links gravitational force to providing the centripetal force, or prevents Europa flying off (reference to curved path or circular motion).
Worked solution
a) The force needed is gravity (gravitational attraction) between Jupiter and Europa.
b) Gravity provides a force towards the centre of Jupiter—this force acts as the centripetal force, keeping Europa in a curved (circular) path. Without this force, Europa would move off in a straight line.