Anonlinear spring model could include a cubic term. that is, the force is approximated by f(x) = –kx + k’x3 . a) if all quantities are in our usual (si) units, what are the units of k and k’? b) for a particular spring, the constants are k = 300 and k’ = 5x104 . how much does the potential energy in the spring change when it is stretched from x = 0.02 m to 0.05 m?

The dipole moment of the water molecule (h2o) is 6.17x10^-30 c. m. consider a water molecule located at the origin whose dipole moment p points in the +x-direction. a chlorine ion ( of charge-1.60x10^-19c , is located at x=3.00x10^-9m . assume that is much larger than the separation d between the charges in the dipole, so that the approximate expression for the electric field along the dipole axis can be used. a) find the magnitude of the electric force that the water molecule exerts on the chlorine ion. b) what is the direction of the electric force. -x-direction or +x-direction c) is this force attractive or repulsive?