Expression : vf2 = select from the variables below to write your expression. note that all variables may not be required. β, θ, a, b, d, g, h, j, k, m, n, p, s, t, v0 part (b) if the slide is 4.0 m long and the child's final speed is vf = 5.0 m/s, what is their initial speed, in meters per second? numeric : a numeric value is expected and not an expression. v0, max = part (c) when starting from rest, how long, in seconds, does it take the child to reach the bottom of the slide? numeric : a numeric value is expected and not an expression.