
Answer
given,
Spring force constant = 120 N/m
mass of the wooden block = 0.27 Kg
coefficient of friction = 0.46
a) we know, Â
  μ N = mg
  0.46 x N = 0.27 x 9.8
  N = 5.75 Newton
This should be the normal force on the block by the wall. Thus minimum spring force should be 5.75 newton.
       F = k x d
k = spring constant,
d = compression in spring)
5.75 = 120 x d
 d = 0.048 m
 d = 4.8 cm
b)  answer will  change if the mass of block is doubled.
mass becomes = 0.54 kg
the normal force  needed = 11.4 newton.
the compression becomes  = 9.6 cm.