ZIMSEC O Level Combined Science Notes: The concept of pressure
 Pressure is the force acting over an area
 In such pressure is usually the force per unit area exerted by a fluid/gas
 over a surface with which it is in contact
 \text{Pressure=} \dfrac{Force}{Area}
 If a big force is exerted over a small area it results high pressure
 An example is the force at the tip of a women’s high heeled shoes
 It is higher than the pressure exerted by flat shoes
 The pressure of high heeled shoes is even higher than that of a man wearing flat shoes
 Even when the man weighs much more than the women.
 The pressure of a stiletto is higher than that of an elephant’s foot!
 As already pointed out the formula for pressure is:
 \text{Pressure=}\dfrac{Force}{Area}
 In unit terms this can be written down as:
 \text{Pa=}\dfrac{N}{m^2}
 Pastands for pascals
 This is the unit for pressure
 Nis for newtons
 m^{2}is the area in square metres
 One Pascal is equal to 1 Newton of Pressure per square meter
 Like most units the Pascal can have prefixes such as 1 kilo pascal (1 000N/m^{2}) or even mega pascals
Example calculations
 A rectangular block with dimensions 100cm x 120 cm x 150cm and weighs 1.5 N.
What pressure does it exert: On its 100cm x 120 cm face
 100cm x 150cm face
 120 cm x 150 cm face
 Solution:

 \text{Pa=} \dfrac{1.5}{1.2}=\text{1.25 Pa}
 \text{Pa=}\dfrac{1.5}{1.5}= \text{1Pa}
 \text{Pa=}\dfrac{1.5}{1.8}=\therefore \text{0.83 Pa}

 A nail is hammered into wood using a hammer of weight 10N. If the nail has an area of 1 mm^{2} at the tip what is the pressure exerted on the wood?
 Solution:\text{Pa=}\dfrac{10N}{0.000001}\text{10000000Pa}
NB Remember to convert the square cm and square mm into square meters
To access more topics go to the Combined Science Notes page
Quick NetOne, Telecel, Africom, And Econet Airtime Recharge
If anything goes wrong, chat with us using the chat feature at the bottom right of this screen