a car moving at 10 m/s speeds up uniformly to a speed of 30 m/s in a time of 5 seconds. What was the car's acceleration?

Answer 1

Initial speed v_o = 10 m/s, final speed v = 30 m/s, time t = 5 s. Use definition of average acceleration, a = (v - v_o) / t = (30 - 10) / 5 = +4 m/s², positive because car is speeding up.