Answer
a) x=0.0565m
b)Not in contact with spring
K=0.57J
Work Step by Step
a)By work-kinetic theorem,
0.5kx^{2}=mgh
0.5(640)x^{2=0.09(9.8)(1.8)sin(40)
x=0.0565m
b)0.0565<0.8, hence it is no longer in contact
0.5(640)(0.5647)^{2}=(0.09)(9.8)(0.8)sin(40)+K
Hence, K=0.57J
