A ball is thrown up; its height is h = 20t - 5t^2 metres. Factorise to find when it lands back on the ground.

  1. t = 4 s
  2. t = 20 s
  3. t = 5 s
  4. t = 2 s
Answer

A) t = 4 s

h = 5t(4 - t) = 0 when t = 0 (start) or t = 4 s (landing). SLO M-09-A-21 · Application

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