A metal sphere with radius r = 1.10 cm is supported on an insulating stand at the center of a hollow, metal, spherical shell with radius r = 9.00 cm . Charge +q is put on the inner sphere and charge −q−q on the outer spherical shell. The magnitude of qq is chosen to make the potential difference between the spheres 400 VV , with the inner sphere at higher potential.

The magnitude of q = 0.612nC

Explanation:

The concept of coulomb's law was applied as it relates to the potential of each surface mentioned in the question. we are considering an inner sphere and a spherical shell each with its own radius.

The potential at each sphere was gotten, thereafter the potential differences between each sphere was equated to get the magnitude of the charge as it is shown in the attached file.

The steps and the mathematical explanation are as shown in the attachment.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.