高中物理問題(friction/energy)

Sorry,物理菜鳥

1)Suppose a large flat plank of wood starts from rest and slides down a hill of slope40*.At the foot of the hill it encounters a second hill of slope30* and starts sliding up that hill.The coefficient of kinetic friction of each hill is 0.3
a)Wt's the acceleration of the plank down the first incline?
b)Wt's the acceleration of the plank as it travels up the second incline?
C)Wt should the minimum of the second hill be if the plank is not to slide down,once it gets to the highest point it reaches on that hill?

2)a)How much does a block of mass 20kg traveling on a smooth surface at 50m/s composs a spring-initially at rest of spring constant 4000N/m upon impact?
b)Suppose that the block in(a)is dropped to the spring from a height of 10m.How much does the spring compress?
3)a)A block of mass 20kg is released from rest at and travel 8m down a smooth surface of inclination30* to the horizontal.It then comes into contact with constact 4000N/m at the smooth,horizontal base of the incline.Wt's the maximum compression of the spring?
B)
if the coefficients of static and kinetic friction between the surface of the incline are 0.3 and 0.2 respectively.(The base level of the incline is assumed to frictionless.)
c)
The coefficients of static and kinetic friction between the block and surface of the incline are 0.35 and 0.25 respectively(The base is smooth)
4)A spring of length 1 and spring contact 2000N/m is attached at the bottom of the inclined surface of U/k=0.2 and U/s=0.25.The spring extends up the 37* incline base.It slides down and hits the spring.
a)Relative to the base of the incline,wt's the K.E. and P.E. of the block when it is released from rest?
b)Wt is the K.E. and P.E. of the block as it comes into contact with the spring?
c)Write an expression for the total energy of the block and spring.When the spring is at maximum compression?
[Don't note to formulate an energy balance equation.]