Your weight is determined by your mass and the pull of gravity. On Earth, gravity is about 9.8 N/kg (usually rounded off as 10 N/kg). The force of gravity causes objects to accelerate towards the centre of the Earth at 9.8 m/s/s (m/s/s is sometimes written as m/s2 or ms-2). In a vacuum, two objects with different masses will accelerate at the same rate and hit the ground at the same time.
Brian Cox has a tendency to throw in a few mind-blowing details. If you ever get asked, “Why does an object fall towards the ground?” You could give his answer of, “because it is following geodesics through curved spacetime”!
For organisms as big as you and me, gravity is the most significant force that affects our daily life. If you are an insect then the electromagnetic force is probably more significant. It allows creatures to grip the smooth surface of a pane of glass or stand on a body of water.
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Questions…
- What force is pulling the feathers to the ground?
- What force opposes the motion of the feathers before the air is extracted?
- Where would you find a natural vacuum?
- What are the two main gases that make up about 98% of air?
- What store of energy does a moving object have?
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