1. The problem statement, all variables and given/known data A 5.0 kg block slides along a horizontal surface with a coefficient of friction µk = 0.30. The block has a speed v = 2.1 m/s when it strikes a massless spring head-on (as in the figure). http://www.webassign.net/gianpse4/8-18.gif (a) If the spring has force constant k = 120 N/m, how far is the spring compressed? (b) What minimum value of the coefficient of static friction, µs, will assure that the spring remains compressed at the maximum compressed position? If µs is less than this, what is the speed of the block when it detaches from the decompressing spring? [Hint: Detachment occurs when the spring reaches its natural length (x = 0).] 2. Relevant equations 3. The attempt at a solution a) -1/2(5.0kg)(2.1m/s)^2 + 1/2(120N/m)(x^2) = (0.30)(5.0kg)(9.8m/s^2)(cos 180)(x) x=0.323m b) I took u(5.0kg)(9.8m/s^2)(0.323m)(cos 180) = -1/2(120N/m)(0.323m)^2 which is not correct. Can someone help me get the correct equation??