Number 7 and 8 show all work

7) A 1.75-kg block starts from rest at an initial height of 40.0 cm and slides down a frictionless circular ramp, as shown in the figure below. It slides for 79.0 cm on the horizontal surface before coming to a stop. What is the coefficient of kinetic friction? Assume that only the horizontal stretch has friction, and the curved portion is frictionless. 40 cm 8) The potential energy shared by two atoms separated by a distance r in a diatomic molecule is given by the Lennard-Jones function (U. and ro are constants): 12 U(r) = Uo 2 -2 (" ) (a) Where is U(r) = 0 ? (b) Show that the minimum potential energy is -Uo and that it occurs at ro. (c) Where is Fr = 0 ? (d) Sketch U(r)