A measurement that both size and direction may be represented by an arrow

Fill in the blank. the number of each type of element in the compound (other than 1) is represented by a small number to the right of the element symbol.

Find the magnetic field a distance r from the center of a long wire that has radius a and carries a uniform current per unit area j in the positive z direction.

Under the action of a constant force an object accelerates at 7.8 m/s2. what will the acceleration be if (a) the force is halved? (b) the object's mass is halved? (c) the force and the object's mass are both halved? (d) the force is halved and the object's mass is doubled?