Does a friction force start things moving or stop things moving ?
It depends. If you roll a tire across the ground, friction will slow and stop it. But if there were not a frictional force between the tires of a car and the road, then when you pushed on the accelerator, your tires would spin and your car would never move. So friction allows the car to start moving. Also, if you put a a marble on a table with a table cloth between the marble and the table and then you slowly pull the table cloth out from under the marble, the marble will begin to move due to friction between the tablecloth and the marble. The answer to your question really depends on where the friction is and what is moving.
