d 0 a ch o D Q of stretching a non-linear spring requires an amount of Work given by the equation U - 154² 10x², Where U is in Joules and (x) is is meters. How much force is required to hold this spring stretched out im from its equilibrium position ?​

In a unit cell of fcc structure, indicate the position of one of the tetrahedral interstitial sites by plotting the corresponding tetrahedron. do the same for one of the octahedral interstitial sites (in a separate fcc unit cell). mark the positions of all the tetrahedral and octahedral interstitial sites in the unit cells. how many equivalent tetrahedral sites and how many equivalent octahedral sites are contained in a fcc unit cell, respectively. what is the coordination number for a tetrahedral site and what is the coordination number for an octahedral site?