A child of a mass m=26kg slides down a slide of height h=2.3m without friction. let gravitational potential energy be zero at ground level. What is an expression for the child's total mechanical energy, E, at the top of the slide, in terms of the variables in the problem and the acceleration due to gravity g. Calculate the change in the child's potential energy, U in joules, from the top to the bottom of the slide at ground level (i.e. U=Uground-Utop). What is the child's final speed, vf in m/s?