A garden lamp post is fabricated by welding a hollow cylindrical pipe to the flat…
MATHEMATICS · Multi-part · GCSE · Mathematics · Geometry and Measures · Geometry and Measures
Problem
A garden lamp post is fabricated by welding a hollow cylindrical pipe to the flat face of a solid hemisphere. The external radius of both the cylinder and the hemisphere is 7 cm. The cylinder is 1.2 m long and the metal thickness is 1 cm (so its internal radius is 6 cm). The open end of the cylinder remains exposed, while the circular faces at the joint are removed before welding.
Use π=722.
(i) Calculate the total outer surface area of the lamp post.
(ii) An anti-rust coating is applied over the entire outer surface at the rate of 75 g per square metre. Find, to the nearest gram, the mass of coating required.