You may have noticed while driving that your car's velocity does not continue to increase, even though you keep your foot on the gas pedal. This behavior is due to air resistance and friction between the moving parts of the car. Figure 2.48 shows a qualitative vx-t graph for a typical car if it starts from rest at the origin and travels in a straight line (the x-axis). Sketch qualitative ax-t and x-t graphs for this car