If the velocity-time graph has the shape AMB, what would be the shape of the corresponding acceleration-time graph?

$$\text{For the first segment from point } A \text{ to the lowest corner point } M:$$ 

$$\text{The curve is a straight line sloping downward from left to right.}$$

$$\text{Slope is constant and negative } \implies a = \text{negative constant.}$$ 

$$\text{For the second segment from the corner point } M \text{ to point } B:$$

$$\text{The curve is a straight line sloping upward from left to right.}$$ 

$$\text{Slope is constant and positive } \implies a = \text{positive constant.}$$

$$\text{Combining both regions results in a step waveform that shifts from a negative to a positive value.}$$