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**1. Homework Statement**

A force of magnitude 39.5N stretches a vertical spring a distance 0.256m.

a) What mass must be suspended from the spring so that the system will oscillate with a period of 1.10s?

got 4.73kg

b) If the amplitude of the motion is 5.00×10−2m and the period is that specified in part (a), where is the object at a time 0.320s after it has passed the equilibrium position, moving downward? (Take the upward direction positive.)

c) What force (magnitude) does the spring exert on the object when it is a distance 2.50×10−2m below the equilibrium position, moving upward?

d) direction of part c's force?

**2. Homework Equations**

T = 2pi/omega

omega = 2pi/T

x = Acos(omegat+phi)

F = kx

F/x = k = 154.3N

T = 2pi(m/k)^1/2

**3. The Attempt at a Solution**

b) x = Acos((2pi/1.10)*.320) = .04998 ~ .05m - incorrect

c) 1. F = kx = (154.3)(2.5x10^-2) = 3.9 - incorrect

2. F = k[tex]\int[/tex]xdx (from 5x10^-2 to 2.5x10^-2)

= -.1446m - incorrect

I don't know why the equations aren't working for me, any help is appreciated.