
Explanation:
Natural length of a spring is
. The spring is streched by
. The resultant energy of the spring is
.
The potential energy of an ideal spring with spring constant
and elongation
is given by
.
So, in the current problem, the natural length of the spring is not required to find the spring constant
.

∴ The spring constant of the spring = 
If F =m*a
and the question says how much force the s needed to accelerate a 68kg skier to a rate of 1.2ms^-2
Then F = 68*1.2
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Explanation:
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