A spring is anchored to some point on a table. The free
end is placed at the origin of a coordinate system 
.
The spring constant is
.
The other end is compressed 
and a mass of 
is
attached to it as shown.
(a) When you let go of the mass it accelerates
towards . What is the velocity of the mass at
? Assume that the table is frictionless.
Hint: use the work energy theorem
(b) Now assume that there is a frictional force of 
between the block and the table. What's the velocity in
this case?
