What indicates that a vehicle is speeding up on a velocity-time graph?

A velocity-time graph displays the relationship between an object’s velocity and time. When the line is slanted upwards, it signifies that the vehicle's velocity is increasing over time. This upward slope indicates positive acceleration, meaning the vehicle is speeding up. The steeper the slope, the greater the acceleration occurring.

In contrast, a horizontal line represents a constant velocity, indicating that the vehicle is neither speeding up nor slowing down. A vertical line would suggest an instantaneous change in velocity, which is not physically realistic in this context. A slanted downward line indicates that the vehicle is decelerating or slowing down. Thus, the slant upwards is a clear indication of the vehicle gaining speed.