Physics
posted by Carden .
A 2.1 kg block slides with a speed of 1.1 m/s on a frictionless, horizontal surface until it encounters a spring.
(a) If the block compresses the spring 5.7 cm before coming to rest, what is the force constant of the spring?
(b) What initial speed should the block have to compress the spring by 1.8 cm?
I know that 1/2kx2 comes into play somewhere. I'm not sure hoe the velocity plays a role in all of this. I'm overall just completely confused.

A) ( 1/2 )kx^2 = ( 1/2 )mv^2
so.. k=mv^2/x^2
(make sure you convert 5.7cm to meters first.)
B) ( 1/2 )kx^2=(1/2)mv^2
so... v^2=kx^2/m
solve for v.