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## Homework Statement

A 500g block on a spring is pulled 20cm and released. The motion has a period 0.8s.

What is the velocity when the block is 15.4cm from the equilibrium?

## Homework Equations

E

_{total}= 0.5kx

^{2}+ 0.5mv

^{2}

w = [tex]\sqrt{k/m}[/tex]

w = 2pi*f

f = 1/T

## The Attempt at a Solution

[FINDING K]

f = 1/0.8 = 1.25

w = 2pi*(1.25) = 7.85

7.85 = [tex]\sqrt{k/0.5}[/tex]

k = 30.8

[FINDING TOTAL ENERGY BY USING THE INITIAL VALUES]

E

_{total}= 0.5(30.8)(0.2)

^{2}

= 0.616

[USING THE TOTAL ENERGY WITH THE SECOND SET OF VALUES TO FIND V]

0.616 = 0.5(30.8)(0.154)

^{2}+ 0.5(0.5)(v)

^{2}

x = 1.7

Make sense to me...just hope its right. Any comments? Thanks as always - I appreciate the effort.