A light platform is suspended from the ceiling by a spring. A student with a mas

Question

A light platform is suspended from the ceiling by a spring. A student with a mass of 74 kg climbs onto the platform. When it stops bouncing and reaches its new equilibrium position (x=0), the student notices that the spring has stretched 0.79 m. The student's friend pulls the platform down 0.29 m further and then releases it at t=0. What is the amplitude of the motion of the student on the platform? What is the maximum speed? At what time does the maximum speed occur?

I have tried a few different things for this question but none seem to be working.

Explanation / Answer

a)

A = 0.29 m

b)

k x0 = m g

==> k = m g/x0 = 74*9.8/0.79 = 917.97 N/m

0.5 k A^2 = 0.5 m v^2

==> v = sqrt(k A^2/m) = sqrt(917.97*0.29*0.29/74) = 1.02 m/s

c)

T = 2 pi sqrt(m/k) = 2*3.1416*sqrt(74/917.97) = 1.78 s

==> t = T/4 = 0.446 s

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