Distance-time graph for stationary then accelerating motion

Steps:

• Student stationary in shop for 5 minutes: distance traveled is zero, so graph flat at s=0.
• After 5 minutes, starts cycling downhill: gravity causes constant acceleration, so distance increases quadratically with time.
• Initial speed likely zero at start of motion, leading to parabolic curve.
• Graph must show horizontal line followed by upward curve.

Why D is correct:

• Matches s = ut + (1/2)at² for constant acceleration from rest after delay, with flat start.

Why the others are wrong:

• A: No initial flat section, assumes motion from t=0.
• B: Flat then straight line, implies constant speed, not acceleration downhill.
• C: Curved from start or wrong shape, ignores stationary period.

Final answer: D