[Force] [Magnets] [Friction] [Gravity and Upthrust]
Gravity is a downward force.
Gravity gives everything weight.
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 direction of a force is always shown by an arrow
that always points away from the object
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)
Here is a diagram of a ball floating on water
There are two forces on the ball
Gravity pulls down and
Upthrust pushes up
If the ball 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
(and sink when the pull of gravity is graeter than the upthrust)