## College Physics (4th Edition)

(a) The speed is $5.0~m/s$ when the stopwatch reads $12.0~s$ (b) The car moves 6.0 meters.
(a) We can find the velocity at $t= 12.0~s$: $v_f = v_0+a~\Delta t$ $v_f = 1.0~m/s+(2.0~m/s^2)(2.0~s)$ $v_f = 5.0~m/s$ The speed is $5.0~m/s$ when the stopwatch reads $12.0~s$ (b) We can find the distance the car moves: $\Delta x = v_0~t+\frac{1}{2}a(\Delta t)^2$ $\Delta x = (1.0~m/s)(2.0~s)+\frac{1}{2}(2.0~m/s^2)(2.0~s)^2$ $\Delta x = 6.0~m$ The car moves 6.0 meters.