An object starts from rest and accelerates uniformly at 4 m/s² for 5 s. What is its final speed?

A) 10 m/s

B) 30 m/s

C) 40 m/s

D) 20 m/s

Answer: D

Explanation: Use final speed = acceleration × time from rest for the stated idealized conditions. Substitution gives 4 × 5 = 20 m/s.