Posted by for "bobpursley" on Friday, November 6, 2009 at 2:53pm.
If a 40 kg brick and a 400 kg brick each dropped from 1 m above a trampoline, find the lowest position of each brick. Assume the trampoline is a simple spring obeying Hooke's law with a k value of 12 000 N/m.
So, I used
mg(h+x)=1/2 k x^2
then solved for x in each case.
and got 2 different values out of the quadratic formula:
0.223 m and 0.0000242 m
given the question, how can I rule one of the answers out and choose the reasonable answer?

Physics  bobpursley, Friday, November 6, 2009 at 3:02pm
6000x^240kx 40*9.8*1=0 where k is 1, or 10
x= (+40k+sqrt(1600k^2+9.4E6)/12,000
for k=1
x= (40+3067)/12000= 25cm ignore the x, it has no physical meaning, the trampoline will not deform upward.
for k=10
x= (+400+sqrt(160000+9.4E6)/12000
x=(400+3093)/12000=29cm
check my math.

Physics  Rachel, Friday, November 6, 2009 at 3:06pm
you lost be. k= 12 000 N/m
where are you getting 1 or 10
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