Non-uniform acceleration shown by changing slope in speed-time graph

Steps:

• Identify acceleration as the gradient (slope) of the speed-time graph.
• Uniform acceleration means constant slope (straight line segment).
• Non-uniform acceleration means varying slope (curved segment).
• Examine each part: straight lines indicate uniform; curves indicate non-uniform.

Why C is correct:

• Part C has a curved line, where slope changes, meaning acceleration varies (non-uniform) per the definition of acceleration as dv/dt.

Why the others are wrong:

• A: Straight increasing line shows constant positive acceleration (uniform).
• B: Horizontal line indicates zero acceleration (uniform).
• D: Straight decreasing line shows constant negative acceleration (uniform).

Final answer: C