The Earth-Moon system has a centre of mass that is not located at the centre of the Earth. Both the Earth and the Moon orbit around this point, also know as barycentre. Build your own planetary system and find out where is the centre of mass.
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Keywords: Rotational mechanics, Doppler effect, Detecting exoplanets, Principle of moments, Torque, Physics, Mathematics, Astronomy
Material:
• 2 or 4 tennis balls
• Strong string
• Scissors
• Marker pen
• Knitting needle or screwdriver
• Ball bearings/lead pellets/small coins – enough to fill one tennis ball
• Strong glue or strong sticky tape
• Sticky tape
• Craft knife
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