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ICSE Class 9 Physics Question 3 of 19

Pressure in Fluids and Atmospheric Pressure — Question 1

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Question 1

A hammer exerts a force of 1.5 N on each of the two nails A and B. The area of cross section of tip of nail A is 2 mm2 while that of nail B is 6 mm2 . Calculate pressure on each nail in pascal.

Answer

As we know,

Pressure (P) = Thrust (F)Area (A)\dfrac{\text {Thrust (F)}}{\text {Area (A)}}

Given,

F = 1.5 N

A = 2 mm2

Converting 2 mm2 in metre2

As 1 mm = 11000\dfrac{1}{1000} m

So, 1 mm2 = (1) mm x (1) mm

= (11000)m×(11000)m(\dfrac{1}{1000}) m \times (\dfrac{1}{1000}) m

= 1 x 10 -6 m2

Hence,

2 mm2 = 2 x 10-6 m2

AA = 2 x 10 -6 m2

AB = 6 x 10 -6 m2

Substituting the values in the formula above, we get,

Pressure on A

P=1.52×10−6P=0.75×106⇒P=7.5×105 Pa\text P = \dfrac{1.5}{2 \times 10^{-6}} \\[0.5em] \text P = 0.75 \times 10^{6} \\[0.5em] \Rightarrow \text P = 7.5 \times 10^{5} \text { Pa} \\[0.5em]

Hence, Pressure on A = 7.5 x 105 Pa

Pressure on B

P=1.56×10−6P=0.25×106⇒P=2.5×105 Pa\text P = \dfrac{1.5}{6 \times 10^{-6}} \\[0.5em] \text P = 0.25 \times 10^{6} \\[0.5em] \Rightarrow \text P = 2.5 \times 10^{5} \text { Pa} \\[0.5em]

Hence, Pressure on B = 2.5 x 105 Pa