physics please help!!
posted by archi .
Hung vertically, a massless spring extends by 3.00 cm when a mass of 992.0 g is attached to its lower end. The same mass and spring are then placed apart on a table. The spring is fixed in place and then the mass is given a velocity of 0.800 m/s towards the spring.
a) What is the maximum compression of the spring when the mass runs into it?
b) After compressing the spring the mass will rebound. What is its velocity just as it leaves contact with the spring?

a, find k. k= mg/x (in change grams to kg, cm to m).
then, 1/2 mv^2= 1/2 k x^2
solve for x, the max compression.
b. it will rebound with a velocity of .800m/s, of course...if the spring is massless.. 
thanks!