https://lh3.googleusercontent.com/0GOyZeQMdpLgYxYwwP4FMabe-Mk7QpADPC4ZK4PVpBGKvamcqjopOf3M0evdhE8PHZ3iTQ=s138 m1 is 4 kg and m2 is 8 kg. The kinetic friction coefficient on the table is 0.3. m1 is held in place. When m1 is released, m2 accelerates 1.2 m to the floor. Use conservation of energy/ and or Work KE principle to find the speed of the two blocks at the instant m2 hits the floor. I used the following equation to solve the problem: PE = KE1 + KE2 + work(friction) with g = 10 m/s2 8x10x1.2 = 1/2 (4) (v2) + 1/2 (8) (v2) + Nx.3x1.2 and then solved for v. I got the right answer but I see work done by friction as negative (the force and displacement are in opposite directions). If I use a negative number here, I get the wrong answer. Also, regarding conservation of energy, I see a change in PE as negative energy (decrease in PE), the friction as negative work and the change in KE for m1 and m2 as a gain in energy. Shouldn't the change in PE + work done by friction = change in KE of m1 + change in KE of m2? Why is work done by friction positive in my original equation?