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Atoms And Molecules

Question
CBSEENSC9006157
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A block of wood is kept on a table top. The mass of wooden block is 5 kg and its dimensions are 40 cm x 20 cm x 10 cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table top with its sides of dimensions (i) 20 cm x 10 cm and (ii) 40 cm x 20 cm.

Solution

Mass of the wooden block  = 5 kg
Dimensions of the block = 40 cm x 20 cm x 10 cm
Force exerted by the block on the table top,
 F = Weight of block = mg = 5 x 9.8 = 49 N
(i) Let us consider the side of dimension 20 cm x 10 cm
Therefore, 
Area = Length x Breadth  = 20 cm x 10 cm
        = 0.20 x 0.10 m = 0.02 m2
That is, 
Pressure space space equals space Thrust over Area space space space space space space space space space space space space space space space space space equals space fraction numerator Force space over denominator Area end fraction space equals space fraction numerator 49 space straight N over denominator 0.02 space straight m squared end fraction space equals space 2450 space Nm to the power of negative 2 end exponent.
(ii) Consider the block lies on its side 40 cm x  20 cm,
Area = Length x Breadth
        = 40 cm x 20 cm
        = 0.40 m x 0.20 m = 0.08 m2

When the block lies on its side 40 cm x 20 cm, it exerts the same force F.
therefore space space space Pressure space equals space Thrust over Area space space space space space space space space space space space space space space space space space space space space space space space equals space Force over Area space equals fraction numerator 49 space straight N over denominator 0.08 space straight m squared end fraction space equals space 612.5 space Nm to the power of negative 2 end exponent.

 

Some More Questions From Atoms And Molecules Chapter

Convert into mole

(a) 12 gm of oxygen gas

(b) 20 gm of water

(c) 22 gm of carbon dioxide.

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(a) 0.2 mole oxygen atoms.

(b) 0.5 mole of water molecules.

Calculate the number of molecules of sulphur (S8) present in 16 gm of solid sulphur.

Calculate the number of aluminium ions present in 0.56 gm of aluminium oxide.

Explain law of conservation of mass.

50 g of 10% lead nitrate is mixed with 50 g of 10% sodium chloride in a closed vessel. After the reaction has taken place, it was found that 6.83 g of lead chloride was precipitated. Besides, the reaction mixture contained 90 g water and sodium nitrate. Calculate the amount of sodium nitrate formed.

Name and explain two important laws of chemical combination ?

What are the postulates of Dalton’s atomic theory of matter?

Hydrogen and oxygen combine in two different ways to produce water and hydrogen peroxide. Which of Dalton’s law does this observation confirm? Explain.

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