A permanent magnet cannot be used in electrical bell .Why?

we can not use permanent magnets in radio and electric bells , because permanent magnets loose their property after some time whereas we can change the properties of electromagnet.

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge