When the three blocks in the figure below are released from rest, they accelerate with a magnitude of 0.465 m/s2. Block 1 has mass M, block 2 has 4M, and block 3 has 4M. What is the coefficient of kinetic friction between block 2 and the table?

Question

jusaquikie · Answer

attachment

jusaquikie · Answer

|dw:1348870732734:dw| Do i need to have the coordinate system i use in X3? i do it to keeo the acceleration all in the same direction. i just don't know if i need to or not.

jusaquikie · Answer

i picked my Coordinate system beacuse block 3 is larger than block 1

jusaquikie · Answer

first equasions i get are 
(x1) FT1-m1g=m1a 
FT1=m1a+m1g =.465M+9.8M=10.3M
(x2) FT3-FT1-Fk=m2a 
(x3) m3g-FT3=m3a
FT3=m3g-m3a = 39.2M-1.86M=37.3
(y2) FN-m2g=0
FN=m2g = 39.2M
3
(x2) (37.3M -10.3M -1.86M)/39.2M = uk = .641

which turns our right lol i was using 39.2M for m2a instead of 1.86M meaning i was multiplying by g and not a. glad i could help.