How large is the average friction force?

How do I sketch a graph of an object that is coasting with no force and no friction?

• At first I had to sketch a graph of an object that was moving with a constant force ( no friction). I had my acceleration vs time graph as a straight, positive line. My distance vs time graph as a positive curved line, and my velocity vs time graph as a positive straight line on an angle. But I'm not sure what my graphs should look like for an object that is "coasting" with no force or friction? What would my a vs t graph be because wouldn't the acceleration be 0? And would my v vs t and d vs t be the same as my first graphs? Also, what would the graphs looks like if there was friction, but still no force? Would my a vs t graph be a straight negative line? Any help would be greatly appreciated. Thank you! Sorry if this doesn't make a whole lot of sense I am half asleep and need to get this done.

• Answer:

  No friction/force? The Distance/Time graph would just show the line moving at a constant gradient, just like the velocity time graph as before. (Since velocity is the same, rate of accumulation of distance will be constant) The Velocity/Time graph would show a positive straight horizontal line, just like the acceleration graph from before. (No force so the velocity stays the same) The Acceleration/Time graph would be at zero, since there is no acceleration (since there's no force being applied to the object) Friction, but no force? The Distance/time graph will show a gradual decrease in gradient, as opposed to the increase in gradient like with the force being applied. This looks like a half-life graph, just imagine skiing down a slope, and that slope loses steepness as time passes by, until you're skiing horizontally. The Velocity/time/ will go down in a uniform fashion. Since friction is applied, the object is losing velocity, and so as long as the force of friction is the same, the rate of decrease in velocity will be constant. The Acceleration/time graph will indeed show negative acceleration. Acceleration is a vector quantity, so acceleration in the direction that it was originally going is negative, however, acceleration in the opposite direction is positive. But to keep things simple, the acceleration graph is at a horizontal line below 0. Hope this helped!