The motion of the Moon around the Earth
Practical Activity for 14-16
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
- Locate the Moon against the background pattern of stars.
- 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.
- 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?"
- 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.
- 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.