1. The problem statement, all variables and given/known data 1. A roller coaster car of mass 1500kg starts a distance H =23m above the bottom of a lopp 15m in diameter. If friction is negligible, the downward force of the rails on the car when it is upside down at the top of the loop is ??? 2. Lou is trying to kill mice by swinging a clock of mass m attached to one end of a massless stick 1.4m in length on a nail in the wall. The clock end of the stick is free to rotate around its other end in a vertical circle. Lou raises the clock until the stick is horizontal, and when mice peek their heads out from the hole to their den, he gives it an initial downward velocity v. The clock misses a mouse and continues on its circular path with just enough energy to complete the circle and bonk Lou on the back of his head. (a) What was the value of v ? (b) What was the clock's speed at the bottom of it's swing ? 3. A pendulum consists of a string of length L and a bob of mass m. The string is brought to a horizontal position and the bob is given the minium initial speed enabling the pendulum to make a full turn in the verticle plane. (a) What is the maximum kinetic energy K of the bob ? (b) What is the tension in the string when the kinetic energy maximum ?? 2. Relevant equations E=K + U 3. The attempt at a solution 1. I guess at the beginning there will only be U=1500*g*23. At the top of the loop E= U ( I am not sure). Thus, we have the E=U=-W= integral of (Fdx). How can I move on from there ?? 2. I am clueless in the way solving this problem. 3. I am kinda confused by :"...the bob is given the minimum initial speed enabling the pendulum to make a full turn in the vertical plane."