| Forces: Gravity and Upthrust |
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[Force] [Magnets] [Friction] [Gravity and Upthrust]
Gravity is a downward force.
Gravity gives everything weight.
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A block of wood resting on the table |
The direction of pull on each of the four men is always towards the centre of the earth. Usually the direction of gravity is always DOWN as shown by the block of wood. Notice that the drection of a force is always shown by an arrow. |
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Whenever something is in water, or trying to float, there is a force called upthrust on it.
Upthrust always pushes UP (just llike gravity always pulls down)
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Here is a diagram of a submarine under water. There are two forces on the submarine. Gravity pulls down and Upthrust pushes up
If the submarine does not move up or down then these two forces are equal. |
An object will float when the push of upthrust is LESS than the pull of gravity |
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