P9

     Dt = 12 s,  Dz = 700 m,    Vf = 116 m/s   

    aav = DV / Dt = (116 + 0)/12 = 9.67 m/s**2 downward

P19

Reading from Figure P18, one obtains

a = 0 at t = 3 s; a < 0 at t = 3.7 s; a > 0 at t = 1.1 s; a = 0 at t = 0.25 s,

P47

Vi = 5 m/s, a = 0.2 m/s**2, Dx = 25 m, Vf = ?

Vf = Vi + a Dt so that Dt = Vf - Vi / a

By definition, Dt = Dx /Vav = Dx /[(Vf + Vi)/2]

Hence, Dx /[(Vf + Vi)/2] = Vf - Vi / a  which can be solved for

Vf**2 = Vi**2 + 50 x 0.2 so that Vf = 5.91 m/s

P81

Find Vi = ? if the ball comes beck in 1 s.

Vf = Vi - gDt

We know Vf = 0 at Dt = 0.5 s so that Vi = 9.8 x 0.5 = 4.9 m/s