Chapter 2 - Kinematics in One Dimension - Exercises and Problems - Page 59: 4

At t = 10 s: $v = 1.25~m/s$ At t = 25 s: $v = 0$ At t = 35 s: $v = -5~m/s$

The velocity is the slope of the position versus time graph. At t = 10 s: $v = \frac{25~m}{20~s} = 1.25~m/s$ At t = 25 s: $v = 0$ At t = 35 s: $v = \frac{-50~m}{10~s} = -5~m/s$