Q) Both the ends of a metallic solid cylinder are semi-spherical. Its total height is 19 cm and diameter of the cylinder is 7 cm. Find the weight of the solid if weight of 1 cm³ of the metal is 4.5 g.

Ans:

Step 1: Let’s make  diagram for our better understanding of the question:

Step 2: Here, we can see that the spherical ends are joined with the cylinder and have similar width.

Diameter of the cylinder = 7 cm

Diameter of the spherical ends = 7 cm

Radius of the spherical ends = \frac{7}{2} cm

Step 3: Given that the total height of the object = 19 cm

Height if the cylindrical part = Total height – 2 x radius of a hemispherical end

(There object has 2 spherical end, one each on left and right side)

= total height – diameter of a hemispherical end

= 19 – 7 = 12 cm

Step 4: Next, the Volume of the object = Volume of the cylinder + 2 x Volume of the hemispherical ends

= π r² h + 2 x \frac{2}{3}

= π r² (h + \frac{4}{3} r)

= (\frac{22}{7}) (\frac{7}{2})^2 [12 + (\frac{4}{3})(\frac{7}{2}]

= (11) (\frac{7}{2}) [12 + (\frac{14}{3})]

= (\frac{77}{2}) (\frac{50}{3})

= (\frac{3850}{6}) cm³

Step 5: Given that the weight of 1 cm³ metal is = 4.5 g

Weight of   (\frac{3850}{6}) cm³ metal will be =  (\frac{3850}{6}) x 4.5

= (\frac{3850}{6}) (\frac{45}{10})

= 3850 x  (\frac{45}{60})

= 3850 x  (\frac{3}{4})

= 1925 x  (\frac{3}{2})

= (\frac{5775}{2})

= 2887.50 gm

= 2.8875 kg

Therefore, the weight of the given solid object is 2.8875 kg.

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