Factors affecting Friction
In which case is the distance covered the minimum? Why is the distance covered by the pencil cell different every time. Try to reason why? Discuss the result.Does the distance covered depend on the nature of the surface on which the cell moves? Could the smoothness of the surface of the cell also affect the distance travelled by it?Friction is caused by the irregularities on the two surfaces in contact. Even those surfaces which appear very smooth have a large number of minute irregularities on them . Irregularities on the two surfaces lock into one another. When we attempt to move any surface, we have to apply a force to overcome interlocking. On rough surfaces, there are a larger number of irregularities. So the force of friction is greater if a rough surface is involved.We see that the friction is caused by the interlocking of irregularities in the two surfaces. It is obvious that the force of friction will increase if the two surfaces are pressed harder. You can experience it by dragging a mat when nobody is sitting on it. and when a preson is sitting on it. Recall your experience when last time you moved a heavy box from one place to another. If you have no such experience, get that experience now. What is easier — to move the box from rest, or to move it when it is already in motion? The force required to vercome friction at the instant an object starts moving from rest is a measure of static friction. On the other hand, the force required to keep the object moving with the same speed is a measure of sliding friction.
Friction - Notes