Page 82 - Genius Kidz Prudence Learning Sc-8

Force = 800 N Area = 2m 2 Examples include :
Force Case where less pressure is desired :
\ Pressure (P) =
Area ! In footwears, in the case of broader heel,
800
= = 400 Pa pressure exerted is less as compared to tip
2
toed heel.
2. Calculate the pressure exerted by a box
resting on a table. The box applies a force of 4.2
N when

(a) It is made to stand on the table

(b) when it is placed on its widest base. The
dimensions of the box are
Broad heal Tipped heel
30 cm × 10 cm × 5 cm less pressure more area more pressure less area
Solution : (a) When the box is made to stand. ! Some cases where more pressure is desired
Area in contact with the table is : Bursting of a balloon is easy by a pin as

10 5 compared to finger. Because in the case of a
= 10 cm × 5 cm = × m
100 100 pin area is less and pressure is more.
= 0.005 m 2
F 4.2 N
\ Pressure exerted = =
A 0.005 m 2

= 840 Pa

In C.G.S. system the unit of pressure is
2
dyne/cm .
Pressure exerted by solids :

Pressure exerted by a solid depends on its area Solids have definite shape so pressure is
of action. More the area, less will be the exerted only on area where force is acted upon
pressure and vice-versa. it.

Activity 2

Liquids exert pressure. Glass tube
Take a pan full of water. Then try and dip in it a small
inverted glass. Do you feel any pressure? Record the
result and report your answer as “liquids exert pressure”
Pan full of water
or “liquids do not exert pressure”. Choose either of the
two.

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