a) A block weighing 9.1N requires a force of 2.8N to push it along at constant velocity. What is the coefficient of friction for the surface? b) A weight "W" is now place on the the block and 8N is needed to push them both at constant velocity. What is weight "W" on the block? This is what I got: Since it is constant velocity, there is no acceleration, therefore Fnet is 0, therefore Ff is 2.8N. Normal force is (9.1)(9.8) =89.18N Formula: Ff=uN 2.8=u(89.18) 2.8/89.18=u Therefore u= 0.031 , but that's not the right answer... Why? what did I do wrong? I take it I need to know a before I can do b?