Question

why does a balloon stick to the wall after it is rubbed on silk cloth

Answer 1

because then the friction increases

Answer 2

Balloon sticks to the wall after it is rubbed against a silk cloth because of 'Static Electricity.'..... It is a phenomenon in which charged particles are transferred from one body to another. If a balloon is rubbed against any cloth like silk , which you mentioned, the balloon will take upon all the charged particles from the cloth. This will make the cloth positively charged and the balloon will become negatively charged. Negative charge of the balloon will make wall to move its negative charges as like charges repel, since negative charges will be removed from the wall, this will result in making wall a positively charged surface and hence balloon will stick to the wall as opposite charges are attracted towards each other.............