An object starts from rest and accelerates uniformly at 3 m/s² for 4 s. What is its final speed?

A) 12 m/s

B) 6 m/s

C) 18 m/s

D) 24 m/s

Answer: A

Explanation: Use final speed = acceleration × time from rest for the stated idealized conditions. Substitution gives 3 × 4 = 12 m/s.