Question #6624a

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Answer 1 · 2018-01-28T14:09:15

Total energy at the top of cliff

$mgh=20000J$
Inserting various values and taking $g=10ms^-2$
$50xx10xxh=20000$
$=>h=20000/(500)=40m$
(matches with the given number in the text.
Half way down $1/2$ of her energy has been converted in to her kinetic energy. If $v$ is her velocity half way down we get
$1/2mv^2=10000$
$=>v^2=10000xx2/50=400$
$=>v=sqrt400=20" ms"^-1$