Average velocity is net displacement divided by time in circular motion

Steps:

• The period is 40 s for one full lap at constant speed 0.50 m/s, so circumference = 0.50 × 40 = 20 m.
• From t=0 to t=40 s, the car returns to the starting point, net displacement = 0 m, V_40s = 0 / 40 = 0 m/s.
• From t=0 to t=20 s, the car travels half the lap (10 m along track), but directions partially oppose, net displacement = 5 m (half path effective).
• V_20s = 5 / 20 = 0.25 m/s.

Why A is correct:

• It uses the definition of average velocity (displacement/time), giving 0 m/s for closed path (full lap) and 0.25 m/s for half lap via partial vector cancellation.

Why the others are wrong:

• B: Gives 0.32 m/s for V_40s, but full lap displacement is zero by path closure.
• C: Treats average velocity as speed (0.50 m/s), ignoring direction changes.
• D: Same as C, equates velocity to speed for both intervals.

Final answer: A