A bullet with a kinetic energy of 400 J strikes a wooden block where the bullet has a mass of 0.01kg. How fast was the bullet moving when it hits the wooden block? Plz show work

answerscientific theory;

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.