A speed time graph shows a car moving at 10 m/s for 10 s. The car's speed constantly decreases until it comes to a stop at 30 s. What describes the slope of the graph from 10 s to 30 s?

In a velocity-time diagram, we can see that the first phase of constant velocity through time is a linear one while the second phase indicating the decelerating action of the car to stop eventually exhibits a downward slope or a negative slope. The line is inclined downward.