Zero Acceleration from Constant Velocity

Steps:

• Acceleration is the slope of the velocity-time graph.
• Identify the section between 10s and 20s on the graph.
• A horizontal line in this interval indicates zero slope.
• Zero slope means constant velocity and thus zero acceleration.

Why D is correct:

• By definition, acceleration is the rate of change of velocity (a = Δv/Δt); if velocity is constant, Δv = 0, so a = 0.

Why the others are wrong:

• A: Slope remains zero, so acceleration does not decrease.
• B: Slope remains zero, so acceleration does not increase.
• C: Acceleration is constant at zero, not a non-zero value.

Final answer: D