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:
\(a=\frac{\Delta v}{\Delta t}\)
where \(\Delta v\) is the variation of velocity and \(\Delta t\) is the variation of time. We see that this quantity corresponds to the slope of the curve in the graph (in fact, \(\Delta v\) represents the increment of the y coordinate, while \(\Delta t\) 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.
