EdEssery
Member
Neal\'s conundrum
Neal McDonald (Watch Leader on Kingfisher 2) posed the following problem to Andrew Preece (fellow crew member and YW journalist) earlier today...
"Neal's watch are always chatting and struggling to answer Neal's conundrums, such as 'does the wind instrument at the top of the mast measure wind velocity or wind force' and 'do your hair and nails stop growing in the Southern Ocean?'. This morning he asked me how much extra rope you would need if you took a rope wrapped around the earth on a diameter and moved it a metre away from the earth all the way around."
My schoolboy maths suggests the answer is 2 pie metres.
My logic goes...
Circumference of a Circle is Pie * Diameter of Circle
Let d = diameter of earth in metres
Let n = the answer we are seeking
(Pie x d) + n = Pie x (d + 2) -- [d + 2 = Diameter of earth plus one metre raised each side]
(Pie x d) + n = (Pie x d ) + (Pie x 2) -- [same equation differently quoted]
n = Pie x 2 -- [subtract Pie x d from each side]
QED
but what's wrong - it feels wrong intuitively - the answer must be a function of d but I can't see it.
Help!
Neal McDonald (Watch Leader on Kingfisher 2) posed the following problem to Andrew Preece (fellow crew member and YW journalist) earlier today...
"Neal's watch are always chatting and struggling to answer Neal's conundrums, such as 'does the wind instrument at the top of the mast measure wind velocity or wind force' and 'do your hair and nails stop growing in the Southern Ocean?'. This morning he asked me how much extra rope you would need if you took a rope wrapped around the earth on a diameter and moved it a metre away from the earth all the way around."
My schoolboy maths suggests the answer is 2 pie metres.
My logic goes...
Circumference of a Circle is Pie * Diameter of Circle
Let d = diameter of earth in metres
Let n = the answer we are seeking
(Pie x d) + n = Pie x (d + 2) -- [d + 2 = Diameter of earth plus one metre raised each side]
(Pie x d) + n = (Pie x d ) + (Pie x 2) -- [same equation differently quoted]
n = Pie x 2 -- [subtract Pie x d from each side]
QED
but what's wrong - it feels wrong intuitively - the answer must be a function of d but I can't see it.
Help!