If 6 J of work is needed to stretch a spring from 9 cm to 11 cm and another 10 J is needed to stretch it from 11 cm to 13 cm, what is the natural length (in cm) of the spring?

Rank the six combinations of electric charges on the basis of the electric force acting on q1. define forces pointing to the right as positive and forces pointing to the left as negative. rank positive forces as larger than negative forces. q1,q2,q3 = positive(+) q1 = + q2 = + q3 = - q1 = + q2= - q3= + q1= - q2= + q3= + q1= + q2= - q3= - q1,q2,q3 = negative