8. What would the shape of the graph be if the speed of the object decreased from 50.0 km/hr at 20 s to 30 km/hr at 40 s?9. What is the acceleration in Problem 8?

We will have the following:
8. The graph will be the following:
9. The acceleration of part 8 will be determined as follows:
First, we determine the equivalency of the velocities, that is
[tex]\begin{gathered} \frac{50km}{h}\ast\frac{1000m}{1km}\ast\frac{1h}{3600s}=\frac{125}{9}m/s \\ \\ \frac{30km}{h}\ast\frac{1000m}{1km}\ast\frac{1h}{3600s}=\frac{25}{3}m/s \end{gathered}[/tex]Then, the acceleration will be:
[tex]a=\frac{(25/3\text{ }m/s)-(125/9\text{ }m/s)}{40s-20s}\Rightarrow a=-\frac{5}{18}m/s^2[/tex]So, the acceleration was of -5/18 m/s^2.