[3 Mark Question Answer]

Question 13 Marks

A swimming pool of width $8\ m$ and length $36 \ m$ is filled with water to a certain height. If the pressure exerted by the water on the bottom of the pool is $30,420\ Pa,$ then find the force acting on the bottom of the pool.

Answer

Area of swimming pool $= 8\ m \times 36\ m = 288\ m^2$
Pressure exerted by water $= 30,420 \ Pa$ Force acting on the bottom of pool $= ?$
We know that,
Pressure $= \frac{force}{area}$
Force $=$ Pressure $\times$ Area
$= 288m^2 \times 30,420 \ N/m^2 [Pa = N/m^2]$
$= 8,760,960\ N$

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Question 23 Marks

A woman stands on high heels concentrating her weight on the tip of the heels. Calculate the pressure exerted by her heels on the ground if the area of contact of each heel is $2 \ cm^2$ and the weight of the woman is $650 N.$

Answer

Area of contact =$=2 \ cm ^2$
Force applied by woman on ground $= 650 N$
Pressure exerted by the heels on ground $= ?$
We know that,
Pressure $=\frac{\text { Force }}{\text { Area }}$
$\Rightarrow P=\frac{650 N }{2 \ cm ^2}$
$=325\ N / \ cm ^2$
$=3250000\ N / m ^2[100 \ cm =1 m ]$

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Question 33 Marks

A motorcycle weighs $1200 N.$ If the pressure exerted by one of its tyres is $120\ Pa,$ then find the area of the tyre in contact with the road.

Answer

Force applied by motorcycle on road $= 1200 N$
$\Rightarrow$ Force applied by one tyre on road $= \frac{1200 N }{2}= 600 N$
Pressure exerted by one tyre $= 120 Pa$
Area of contact of the tyre $= ?$
We know that, Pressure $=\frac{\text { Force }}{\text { Area }}$
$\Rightarrow$ Area $=\frac{\text { Force }}{\text { Pressure }}=\frac{600 N }{120 N / m ^2}$
$=5 m ^2$

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PHYSICS [3 Mark Question Answer]

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