Calculate Maximum Spring Compression: 0.4 kg Object, 80 N/m Constant

[cooney88]

Q. An object of mass o.4kg slides at 8m/s across a frictionless path before striking one end of a spring that is fixed at the other end. the spring constant is 80N/m. the maximum distance, in metres, by which the spring compressed is : ans?




I a not sure wether to use hookes law (f=ks) or the kinetic energy formula Ek = .5kmv^2

when i used hookes law i got an answer of 0.04 but when i use the kinetic energy forumla i got 0.57. I know it doesn't really make any sense to use hookes law as u can't find the force, only the momentum (0.4x 8)

any help with this would be greatly apreciated

The Attempt at a Solution

 

[Doc Al]

It sounds like you're answering your own question.

 

[cooney88]

so its the kinetic formula cos it wouldn't make sense to use the hookes law right? but since when can u have the spring constant in a kinetic energy formula?

 

[Doc Al]

so its the kinetic formula cos it wouldn't make sense to use the hookes law right?

Yes, you'll need to use energy conservation.

but since when can u have the spring constant in a kinetic energy formula?

Consider the potential energy stored in a compressed spring--that's where the spring constant appears.

 

[cooney88]

cheers buddy

 

[cooney88]

doc al could you take a look at my query please: its doing my head in. https://www.physicsforums.com/showthread.php?t=314056