A set of crash tests consists of running a test car moving at a speed of 12.4 m/s (27.7 miles/hour) into a solid wall. Strapped securely in an advanced seat belt system, a 57.0 kilogram (126 lbs) dummy is found to move a distance of 0.720 meter from the moment the car touches the wall to the time the car is stopped. Using the direction of motion as the positive direction, obtain the average acceleration of dummy during that time (in g's, with 1g =9.81m/s2).