Follow the clues and solve the terms you have learned.
Across :

1. The friction acting when one body rolls over the surface of another body $(7, 8)$.
4. The frictional force exerted by fluids $(5, 8)$.
6. The overlapping or fitting together of tiny hills and grooves in the form of irregularities on two surfaces in contact.

Down:

2. A bearing that permits rolling between moving and fixed parts by means of small metal balls confined between outer and inner rings, which reduces friction $(4,7)$.
3. Substances that reduce friction.
5. The friction acting when one body slides over the surface of another body $(7,8)$ .
7. The force required to overcome friction at the instant an object starts moving from rest $(6,8)$ .