A 2 kg mass starts from rest with an acceleration of 3 m/s^2 for 5 seconds. What is its final velocity?

• A. 15 m/s
• B. 5 m/s
• C. 10 m/s
• D. 20 m/s

Answer: (A)

With constant acceleration, velocity changes by a times the time interval, starting from the initial velocity: v = v0 + a t. Since the mass is not needed here, focus on motion: the object starts from rest, so v0 = 0. The acceleration is 3 m/s^2 and it acts for 5 seconds, giving v = 0 + (3)(5) = 15 m/s. The other numbers would require a different acceleration, a nonzero starting velocity, or a different time; given the data, 15 m/s is the final velocity.