Ex 12.2, 6
A solid iron pole consists of a cylinder of height 220 cm and base diameter 24 cm, which is surmounted by another cylinder of height 60 cm and radius 8 cm. Find the mass of the pole, given that 1 cm3 of iron has approximately 8g mass. (Use π = 3.14)
To find mass of pole,
we need to find volume of pole
Volume of pole
= volume of small cylinder
+ volume of large cylinder
Volume of small cylinder
Radius = r = 8 cm
Height = h = 60 cm
Volume of small cylinder = 𝜋𝑟2ℎ
= 3.14×(8)2×(60)
= 3.14×64×60
= 12057.6 cm2
Volume of large cylinder
Height = h = 220 cm
Radius = r = Diameter/2 = 24/2 = 12 cm
Volume of large cylinder = 𝜋𝑟2ℎ
= 3.14×(12)2×220
= 3.14×144×220
= 99475.2 cm3
Now,
Volume of pole = Volume of small cylinder + Volume of large cylinder
= 12057. 6 + 99475.2
= 111532.8 cm3
Given that,
1 cm3 of iron has 8 g mass.
So, 1 cm3 of iron has mass = 8 g
So, 111532.8 cm3 cm3 of iron has mass = 111532.8 × 8 g
= 892262.4 g
= 892262.4/1000 kg
= 892.2624 kg
= 892.26 kg

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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