AQA AS Level Physics Paper 2, June 2023: Question 10

✅ Correct Answer: Option A

Option A is the correct choice because velocity is a vector. As the football moves upwards, it has a positive velocity that decreases linearly at a constant rate due to gravity. At the highest point, its vertical velocity is zero. As it falls back down, its velocity becomes negative (moving in the opposite direction) and continues to decrease linearly until it hits the ground.

💡 Key Knowledge

• Vector Nature: Velocity has both magnitude and direction. Upwards is conventionally taken as positive (+), and downwards as negative (-).
• Constant Acceleration: Acceleration due to gravity ( g ) is constant ( 9.81 m s⁻² downwards), meaning the gradient of a v-t graph ( dv/dt = a ) must be constant and negative.
• The Intercept: The line crosses the time axis ( v = 0 ) precisely at the peak of the football's flight path.

🧠 Exam Technique

• Check the y-axis label carefully ( v for velocity, not speed).
• Eliminate magnitude-only graphs immediately if the object changes direction. Speed-time graphs (like Option B) can never cross below the time axis.
• Look at the gradient: Since a = -g throughout the motion, the line must have a single, unbroken, constant negative gradient from start to finish.

❌ Common Errors

• Choosing B: Confusing velocity with speed. Speed cannot be negative, but vertical velocity *must* change sign when direction reverses.
• Choosing C: Assuming acceleration changes or that velocity-time relationships for projectiles are parabolic (parabolas represent displacement-time graphs under constant acceleration, not velocity-time).
• Choosing D: Thinking that the downward journey is a "fresh start" with a positive speed increasing from zero.