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AS Daily A Level Physics question

2025-10-01 OCR A Forces and Motion (Module 3.1 — Motion) 3.1.2(a)(i)

Two identical balls are thrown at the same instant from a balcony with the same speed: one straight up and the other straight down. Air resistance is negligible. Which statement must be true when they reach the ground?

  1. A The upward-thrown ball reaches the ground later and with a lower speed than the downward-thrown ball.
  2. B The downward-thrown ball reaches the ground earlier and with a higher speed because gravity adds to its initial motion.
  3. C Both reach the ground with equal speeds, but the upward-thrown ball takes longer to arrive. (correct)
  4. D Both reach the ground at the same time because their initial speeds are equal in magnitude.

Answer

The correct answer is C.

Correct: C — Both reach the ground with equal speeds, but the upward-thrown ball takes longer to arrive. They start with the same speed from the same height, so the total drop in gravitational potential plus identical initial kinetic energy gives the same impact speed; the upward-thrown ball spends extra time rising before falling back. A The upward-thrown ball is later, but not slower at impact; neglecting air resistance, impact speeds are equal. B Earlier is true for the downward-thrown ball, but its impact speed is not higher; both have the same speed on reaching the ground. C Correct, equal impact speeds with a longer time for the one thrown upward. D Equal initial speeds do not imply equal arrival times; the upward-thrown ball takes longer because it first moves against gravity.

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