Pressure

• Natuurkunde
• Middelbare school
• havo, vwo
• Leerjaar 2,3

Pressure

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You can convert metric units for distance, area and volume

You can use the formula for pressure in different situations

Pressure

To sit on a nail is painful...

for obvious reasons.

But when you sit down on 1000 nails,

you hardly feel anything anymore.

This is because the gravitational force is

equally shared over a large surface.

Pressure

Pressure=​on a surface​​Force​​

P=​A​​F​​

​(m​2​​)​​​​​(N)​​

Calculation skills

Watch these videos if you are having trouble with

• converting units
  
  
• cinvert areas and volumes
  
  
• forgot how to use formula's

Pressure example

When you dive a force of a larger surface, it will hurt less because of a smaller pressure. 

In this example you can put a block on side A or B. The surface for side B is 4 times as big as the surface of side A. This means that the experienced pressure for side B will be 4 times less as well.

It helps when you make a little drawing when you need to convert areas from cm2 to m2. It will give you a quick insight by how much you need to multiply or devide to convert the unit.

Falling through ice

This often ends fatal..

But there is something you can do.

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Therefore prepare and spread your weight as much as possible when moving over the ice.

Example question

Shufling over the ice on your stomach will make a big difference as you will found with this example.

In this question the trick is not to forget that you have two feet instead of one.

5 Steps

GIVEN

ASKED

FORMULA

CONVERT UNITS

CHECK 1 UNKNOWN & CALCULATE

Pressure in a liquid

The pressure in a liquid is equal everywhere.

Because of the constant relationship between force and surface in the equation, the pressure of the liquid will cause a bigger force near the larger cilinder (B).

Although there is more force on cilinder B, it will travel more slowly

Assignment: Thumbtack

A force of F = 1,5 N is exerted on the topside of a thumbtack.

The topsurface is A = 0,65 cm2

The surface of the needle is A = 2,1 mm2

To push the thumbtack into a bulletin board you need a pressure of 106 Pascal

a) Calculate if you can push the thumbtack into the board.

b) Calculate the minimal force needed for this

The thumbtack

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