A 50kg person standing still in ice skates throws their helmet to the right at 25 m/s while on a frictionless surface. This gives the person a speed of 1.0m/s leftwards. What is the mass of the helmet? Consider rightward as the positive direction.

prndulum needs thread, weight clock to time swings

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.