Friction
Friction
Friction is a force that always acts on all moving objects. The force of friction acts between the object and the surface.
E.g; A ball rolling on ground gradually slows down and comes to rest due to force of friction between the ball and the ground.
Causes of friction
Friction is caused by the irregularities on the two surfaces in contact.
We are able to walk because of the force of friction.
Nature of surfaces for friction
Smooth surface: less friction
Rough friction: greater friction
Example where friction is useful
- Walking
- Handling any object
- rolling motion of ball or wheel.
Kinds of friction
1 Static friction
It is a type of frictional force which acts between the surface of two objects when they are kept at rest about each other.
Example: Heap of books resting on a coffee table.
A t-shirt hanging on a hanger.
2 Sliding friction
Sliding friction can be defined as a friction which is generated between the surfaces of any two objects when they are in a sliding motion against each other.
Example: pushing an object along any surface.
Opening of a door or window.
3 Rolling friction
Rolling friction is friction that acts an object when they are rolling over a surface.
Example: A soccer ball rolls along the ground, it will come to a stop because the rolling friction acts in the opposite direction to the motion of the ball.
4 Fluid friction
Fluid friction is friction that acts on objects that are moving through a fluid. A fluid is a substance that can flow and take the shape of its container.
Example: movement of fishes in water.
Friction can be reduced by using:
Grease, oil, powder, ball bearing etc.
Using anti-friction alloy.
Friction can be increased by making a surface rough.
Friction can increased by increasing the roughness of the surfaces which are coming in contact.
The sole of the shoes and the tyers of the vehicles are treated to increase friction.
EXAM RELATED QUESTIONS
- Which type of surface produces less friction?
Ans. Smooth surface produces less friction.
- Which type of surface produces more friction?
Ans. Rough surface produces more friction.
- Explain why sportsmen use shoes with spikes?
Ans. Spikes increases friction and give better grip with the ground. It avoids slipping of sportsmen while playing or running.
- The handle of a cricket bat or a badminton racquet is usually rough. Explain the reason?
Ans. To have better grip on bat it should be rough surface decreases the friction and allow to have a firm grip on bat.
- Explain why objects moving in fluids must have special shape?
Ans. Moving objects in fluids must have special shapes because the drag force or the friction force depends of the shape of the objects.