The motion of the Moon around the Earth
This shows an everyday example of circular motion, the Moon going round the Earth.
Apparatus and materials
Chart showing the star pattern
Health & Safety and Technical notes
a Locate the Moon against the background pattern of stars.
b Follow the Moon’s motion by observing its position relative to the stars at different times on the same night, and also at the same time on consecutive nights.
1 Questions to ask: Is the motion of the Moon around the Earth a natural motion? Is the Moon in equilibrium? Is any force needed to keep it going? Does the Earth attract or repel the Moon?
2 The speed of the Moon is constant but its direction of motion changes constantly, so the velocity is changing. The Moon is not in equilibrium; there must be a force to create this acceleration. The Earth gravitionally pulls the Moon inwards, and keeps it in a stable orbit.
3 Newton’s third law says that the Moon must pull the Earth towards it. This could be linked to the tides, if this has been covered already.