Question 9
On a motor car, which part is designed so that the friction there is as small as possible?
The right answer is the one marked above.
The wheel bearings. Balls are placed between the rotating and non-rotating parts precisely so that they roll instead of rubbing, and the bearings are greased as well.
The other three all need friction to be large: treads to grip the road, and the pads and disc to stop the wheel turning. The same car manages friction differently in different places.