Decreasing speed on a velocity-time graph

Steps:

• Magnitude of velocity equals speed, |v|.
• Speed decreases where |v| reduces over time.
• In positive v region (P), negative slope means decreasing |v|.
• In negative v region (R), positive slope (towards zero) means decreasing |v|; Q shows increasing |v|.

Why B is correct:

• P and R match regions where d|v|/dt < 0, by definition of deceleration for speed.

Why the others are wrong:

• A: Includes Q, where speed increases.
• C: Excludes P and R, where speed also decreases.
• D: Excludes P, where speed decreases.

Final answer: B