1. A. 6.00 sec
The graph shows the velocity of an object (y-axis) versus the time (x-axis). In order to find when the magnitude of the velocity reaches 36.00 km/h, we should find the time t (x-coordinate) at which the velocity (y-coordinate) is 36.
By looking at the graph, we see that this occurs when t=6.00 s.
2. A. positive acceleration
In a velocity-time graph like this one, the slope of the curve corresponds to the acceleration of the object. In fact, acceleration is defined as:
[tex]a=\frac{\Delta v}{\Delta t}[/tex]
where [tex]\Delta v[/tex] is the variation of velocity and [tex]\Delta t[/tex] is the variation of time. We see that this quantity corresponds to the slope of the curve in the graph (in fact, [tex]\Delta v[/tex] represents the increment of the y coordinate, while [tex]\Delta t[/tex] represents the increment of the x coordinate). So, a positive slope means a positive acceleration: in this case, the slope is positive, so the acceleration is also positive.
