springs

[mathmathmath]

physics 12 question. i hope the question is appropriate for the forum.

"an engineer is designing a spring to be placed at the bottom of an elevator shaft. if the elevator cable should break at a height h above the top fo the spring, calculate the value that hte spring constant k shoudl have so that passengers undergo an acceleration fo no more than 5.0g when brought to rest. Let M be the total mass of the elevator and its passengers."

thanks!

btw the answer shuld be 12(Mg/h)

[Harmony]

I think this may be the method.
First calculate the maximum force which the passenger may undergo.(F=ma)
Calculate the potential energy of the spring.
Bear in mind that 0.5Fx=0.5kx^2
If my method is wrong, please correct me.