Question

A golf ball has diameter equal to 4.2 cm. Its surface has 200 dimples each of radius 2 mm. Calculate the total surface area which is exposed to the surroundings assuming that the dimples are hemispherical.

Answer 1

Surface area of ball

`=4pir^2`

`=4pi (4.2 /2)^2`

`= 17.64 pi cm^2`

Total surface area exposed

SA of ball `- 200 (pir^2 - (4pir^2)/2)`

`=17.64 pi - 200 pir^2`

`=17.64 pi -8pi`

`= 80.5 cm^2`