How does the friction affected by the nature of surface?
Take two bricks; one is wrapped in jute while other is wrapped in polythene. Which one will be easy to drag and why?
Why is it easy to drag a mat from the floor, but it is difficult to drag the mat when some body is sitting on it?
What is static and sliding friction?
Which is smaller static friction or the sliding friction and why?
What happens, if the floor we walk on is friction less?
Why is it not easy to move an object from its static position?
Why we could not write with chalk if there were no friction?
The soles of our shoes get worn out after a period of time. Explain why.
Answer:
It is a device used for measuring the force acting on object. It contains a coiled spring. The spring gets stretched when a force is applied on it. Stretching of the spring is measured by a pointer moving on a graduated scale. The reading on the scale gives the magnitude of force.
Nature of surface is a major factor which affects the friction. When we try to move any thing on any surface, we have to apply a force to overcome the interlocking of the surfaces. On rough surfaces, there are a larger number of irregularities. So the force of friction is greater if a rough surface is involved. For example pulling a suitcase on rough floor is more difficult than that of smooth marble floor.
It is easy to drag the brick which is wrapped in polythene. Polythene has smooth surface. So it has less friction than the jute. Thus, it requires lesser force to drag it. Jute has rough surface so it needs more force to drag it.
Friction is caused by the interlocking of the irregularities in the two surfaces. Now the force of friction will increase, if the two surfaces are pressed harder. So it is easy to drag a mat no body is sitting on it, but when a person is sitting on it then it produces more friction so it becomes difficult to drag it.
The force required to overcome friction at the instant an object starts moving from rest is a measure of static friction and the force required to keep the object moving with the same speed is a measure of sliding friction.
When the object starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly smaller than the static friction.
We would not be able to walk on the surface or floor if there is no friction. It is the friction only that helps us to stand or walk on the surface or floor. The grooves of our feet or shoes locked into the irregularities of the floor and make us stand and walk.
When an object is in rest, it has better hold of the surface or floor or ground on which it is placed. In the static position the irregularities of the surface are interlocked properly due to which more force is required to over come the friction. So it is not easy to move an object from its static position.
We could not write with chalk, pen, pencil if there were no friction. If we try to write with chalk or pen or pencil on a friction less surface then no chalk particles stick to the surface. So we will not be able to write. When we write with chalk on the blackboard, its rough surface rubs off some chalk particles which stick to the blackboard and we can see what is written on the board.
It is due to friction. When we walk on the road, then the friction arises. Our shoes has to overcome this friction to walk due to which our shoes get worn out slowly by repeated application of force to overcome the friction caused by the surface or floor or road on which we walk.
