The Open Door Web Site
Mass and Weight
In everyday-life we do not always make a distinction between the mass and weight of an object. However, in science, we must make this distinction because mass and weight are not the same.
This is the measure of the amount of matter (solid, liquid or gas), in a substance.
Mass is measured using a balance and is measured in the SI unit the kilogramme (kg). Since the mass depends on the the amount of matter in an object, it is a constant.
Therefore, mass remains the same wherever it is on the Earth, on the Moon or on Mars.
The Moon's Mass
This is responsible for the gravitational pull of the Moon.
The Moon is approx. ¼ of the Earth's diameter and so we could assume that its pull of gravity should be approx. ¼ of the Earth's. However, from experiments performed on the Moon's surface, we know that its centre is not made of as much nickel and iron as the Earth's : as a consequence, the pull of the centre of the Moon is 1/6 of the Earth's gravity. Imagine the Olympics taking place on the Moon!
The Moon's Gravity
Galileo performed an experiment from the top of the Leaning Tower of Pisa ; where two balls of different masses were dropped. These two balls hit the ground at the same time. Neil Armstrong repeated Galileo's experiment on the Moon's surface. He dropped a hammer and a large feather, an ostrich feather, I think. Since there is no atmosphere and therefore no air resistance; the feather and hammer hit the Moon's surface at the same time!
The Open Door Web Site is non-profit making. Your donations help towards the cost of maintaining this free service on-line.
Donate to the Open Door Web Site using PayPal