2008年2月3日 星期日

8.2 Pressure






What is pressure?

pressure is the amount of force that acts on on a given area of an object.
ex: which has more pressure?
a)dull pencil b)sharp pencil


How does pressure affect matter?

Pressure can cause a gas to be compressed.
ex: if you squeeze or press down a balloon, the shape of he balloon changed.

#The increased pressure on the balloon pushes the air particles closer together.

Compression is a decrease in the volume of matter cause by force.
When pressure is applied to matter , compression can result.

Deformation means a change of shape without being forced into a smaller volume.


what happeneds when a gas-filled container explodes?

The particles of a gas move faster and farther apart when energy is added? ans: it expands

The heated gas exerts more pressure on the inside of the container .
this added pressure can lead to an explosion.


How is pressure measured?

pressure=force/area
units for force and area:

force is measured in newtons(N).
area is often measured in square metres.
pressure is measured in units of newtonsper square metres.

A pressure that is equal to 1N/m2 is called a pascal.
pascal=Pa . This is a very small amount of pressure.

Pressure is often measured using a unit equal to 1000 Pa.
1ooo Pa=1 kilopascal(kPa)





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