## Essential University Physics: Volume 1 (3rd Edition)

a) $-2.5x^2+.5x^4$ b) $x=.7m,2m$
a) We know that the potential energy is equal to the negative integral of the force with respect to distance. Thus, it follows: $U=\int(-5x+2x^3)dx=-2.5x^2+.5x^4$ b) The turning points will occur where U equals -1. Thus, we find: $-1 = -2.5x^2 +.5x^4$ $x=.7m,2m$