Hello guys. I have a test in a couple of days, so I am hoping to get some practice. I'll post any questions I have here, I would appreciate if you guys can help me clear up any confusions. 1. A 400-N block is dragged along a horizontal surface by an applied force F as shown. The coefficient of kinetic friction is uk = 0.4 and the block moves at constant velocity. The magnitude of F is: attempted solution: Since the block moves with constant velocity: [tex]\sum F = 0[/tex] Since [tex]\sum F = ma[/tex] [tex]F_y - mg = ma = 0 [/tex] [tex]F_x - u_kmg = ma = 0 [/tex] The correct answer is 150 N, but obviously the components above are far greater because mg = 400 N. I must be missing something conceptually simple... Please help.