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Find the value of the spring constant.

i did:

W=Fd

F=W/d

F= 18.75N

then i used:

k=F/x

k=18.75N / .16m

k=117.1875N/m

and its not right... i also tried diving the 18.75 by .32m and it still isnt right

problem 2.)

A 30.0g bullet strikes a .607 kg block attached to a fixed horizontal spring whose spring constant is 6.7E3 N/m and sets it into vibration with an amplitude of 21.3cm. What was the speed of the bullet before impact if the two objects move together after impact?

I went on to use:

1/2(mass of bullet)v^2 = 1/2kA^2

solved for v

v=sq.rt.(((6.7E3N/m)(.213m)^2)/.03kg)

v= 100.659

and it isnt right..dont know where to go from here

problem 3.)

A bunjee jumper with mass 69.0kg jumps from a high bridge. After reaching his lowest point, he oscillates up and down, hitting a low point eight more times in 34.9s. He finally comes to rest 22.0m below the level of the bridge. Calculate the spring constant of the bungee cord. Calculate the unstretched length of the bungee cord.

I started out by find the persons force downward but now have no clue where to go from here. I cant even fathom how to set it up...my guess is that i need to do something with dividing the time out into 8 pieces...i have no clue...

any help would be awesome - thanks. also, this is an algebra based physics course so no calculus ;)