Category : 8th Class
Friction
· Friction is a force that opposes the motion. It acts on both the surfaces.
· Friction depends on the nature of surfaces in contact.
· The factors that affect friction are:
(a) the condition of the surfaces in contact and |
(b) the weight of an object. |
· For a given pair of surfaces friction depends upon the state of smoothness of those surfaces.
· Friction depends on how hard the two surfaces press together.
· The force required to overcome friction at the instant an object starts moving from rest is a measure of static friction. The maximum value of static friction, when motion is impending, is sometimes referred to as limiting friction.
· The force required to keep the object moving with the same speed is a measure of sliding friction. It comes into play when an object is sliding over another. Sliding friction is smaller than static friction.
· When one body rolls over another body, rolling friction comes into play. Rolling friction is smaller than the sliding friction.
· Friction is a necessary evil. If friction force is not present, it becomes almost impossible to stop a moving object.
· Friction is sometimes useful and sometimes it is undesirable.
· Friction can be increased by
(i) treading |
(ii) scratching |
(iii) making a surface rough. |
· The sole of the shoes and the tyres of the vehicle are treaded to increase friction.
· Friction can be reduced by
(i) using lubricants |
(ii) using wheels |
(iii) using ball bearings in machines. |
· Fluids exert force of friction on objects in motion through them. The frictional force exerted by fluids is called drag.
· The frictional force on an object in a fluid depends on three factors ?
(i) speed of the object with respect to the fluid |
(ii) shape of the object and |
(iii) the nature of the fluid. |
· Fluid friction can be minimised by giving streamline shapes to bodies moving in fluids.
You need to login to perform this action.
You will be redirected in
3 sec