X(t) = 20-4t²
then what is average velocity
in between t= 0 and t=20sec

v = -80 m/s

Explanation:

Given,

The initial time of a body, t = 0

The final time of the body, t =20 s

The displacement function of the body is given by the relation,

                                X(t) = 20 - 4t²

Therefore, the velocity function is by differentiating the above equation with respect to the function 't'

                                 X'(t) = -8t²

Then,

1)   t = 0 s

                                X'(0) = -8(0)²  

                                        = 0 m/s

2) t = 20  s          

                              X'(20) = -8(20)²

                                         = -160 m/s

The average velocity is given by averaging the initial and final velocity,

                                  V =  -160/2

                                     = -80 m/s

Hence, the average velocity of the given function is, v = -80 m/s