experts pls ca u check .?

Question

now imagine theres a point A at height of 40 metres . now from that point a thin non elastic lace (thread) starts to materialize(magically orignate) and run down and hits the ground due to gravity. the lace keeps on appearing and its like endless. now when it appears at point A its velocity is zero but it gets jerked up to a velocity . now what would be the vellocity of the lace when hits the ground after runnin down 40 metres. AIR RESISTANCE IS TAKEN AS ZERO. here gravity is acting on the vertical length of the lace which is forty metres. according to me the lace can have a maximum velocity of only 20 m/s. which is less than 28 m/s when u drop something from a height of 40 metres..

now for 1000 metres of lace (thread ) to run down originating from that point A, how long will it take..>? hope ppl get my question
heres anotherway of pttin the question.......

ok forget that that point A. take some 1000 metres of chain or lace to a table which is forty metres high . and now throw down one end of lace or chain. remember the lace is neatly arranged and not etangled . now one starts running down ad hits the ground and begins to pull down the rest of the chain which is at a height of 40 metres on top the table. it ill take some time for the whole length(1000m) to run down. relate both the descriptions to get a clear picture . could you answer my question now.?

ok do you think the p.e gained when you lift 1000 m of lace to eght of 40 m . instead o letting it run down like a stream of water , u drop it as a whole every particle of lace would be hiiting the ground at 28 m/s. instead of 20m/s in the run-down method. only half of the p.e can be recovered.

Answer 1

So 40 metres of string (let's say mass m) falls off a support 40 m above the ground, and slowly unwinds. At the moment when the last bit of string leaves the support, the centre of mass is 20 m below the support.

Loss of GPE = m x g x 20m.

Gain in KE = 1/2 x m x v^2

So 20g = 1/2 v^2 and v = square root of (40g), or about 20 m/s.