This isn't really homework because I'm not doing it for school. I'm on my holidays at the moment, and I'm trying to do a bit of Physics on my own. As you can imagine, I have not gotten far, and am stuck on this problem: A stone slides in a straight line across a frozen pond. Given that the initial speed of the stone is 5m/s and that it slides 20m before coming to rest, calculate the coefficient of friction between the stone and the surface of the frozen pond. The deceleration of the stone is (20*2)/5 = 8 m/s2. How should I proceed next? EDIT: I'm really confused. Is the resultant force = 8 X mass? Is the resultant force = frictional force - forward force? I know that frictional coefficient = Frictional force/contact force. However, I've done the algebra and it comes out very messy.