X (t) = (20-4t^2) m, then what its average velocity in between t=0 and t=2sec?

- 8 m/s

Explanation:

average velocity = Δx / Δt = [x2 - x1] / [t2 - t1]

t2 = 2 sec, t1 = 0 sec

x2 = x (2) = 20 - 4 * 2² = 20 - 16 = 4 m

x1 = x (1) = 20 - 4*0² = 20 m

average velocity = Δx / Δt = [4 m - 20 m] / [2 s - 0 s] = - 16 m / 2 s = - 8 m/s