Putting a piece of iron or steel inside the coil makes the magnet strong enough to attract objects. The strength of an electromagnet can be increased by increasing the number of loops of wire around the iron core and by increasing the current or voltage.
No, the ball keeps moving forward due its momentum.
A net force causes an object to accelerate, which means it speeds up, slows down, or changes direction. A bowling ball does not speed up after you let go, so there is no forward force.
