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Re: [Phys-l] Accelerating automobile

On Jan 6, 2008 9:47 AM, LaMontagne, Bob <RLAMONT@providence.edu> wrote:
The statement is that the frictional force between the tires and road "propels" the automobile (in the f=ma sense). I would think that a student would have a hard time justifying that for what is essentially a static friction force.

Is the issue here about static friction forces "propelling" the
automobile? Maybe it would help to show another example where static
friction does something similar (i.e "propelling" some mass m):

Place one book on top of another book on top of a tabletop. Push the
initially resting bottom book slowly. Consider the motion of the top
book. Draw the force diagram for the top book.


-Krishna