## College Physics (4th Edition)

The correct answer is: B. $6.7~m/s$
We can find the speed of the $0.50~kg$ ball after the acceleration period: $v_f = v_0+at$ $v_f = 0+(10~m/s^2)(2.0~s)$ $v_f = 20~m/s$ We can use conservation of momentum to find the final speed $v$ of the balls after the collision: $(0.50~kg+1.0~kg)~v = (0.50~kg)(20~m/s)$ $v = \frac{(0.50~kg)(20~m/s)}{1.5~kg}$ $v = 6.7~m/s$ The correct answer is: B. $6.7~m/s$