You are asked to calculate an object's velocity, in order to do so you must know the object's direction and speed. distance and time. speed and distance. direction and distance.

You are asked to calculate an object's velocity.

In order to do so, you must know the object's speed and the direction

in which it's moving, or you must have other information that makes it

possible for you to calculate its speed and direction.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.