Question

Why does the unit of time enter twice in the unit of acceleration?

Answer 1

Please find attached photograph for your answer.

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Answer 2

Constant Acceleration is (Vf-Vi)/t so the unit for velocity is m/s and unit for time is seconds then unit for acceleration is m/s times 1 s which equals m/s/s or m/s^2
Remember acceleration is the change of speed in velocity