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Cat and mat.

posted Feb 2, 2015, 12:14 AM by Ranmini Perera   [ updated Dec 3, 2015, 12:16 PM by Upali Salpadoru ]


If a cat sits on a mat, 
when you pull the mat 
will the cat also come?  

Idiot:  " No! It will go away".

You don’t need a cat and a mat to find this out.

 We can substitute a coin for a cat and a strip of paper for a mat.The  coin is on a strip of paper  standing on its edge. The paper is jutting out of the table.  You have to take a ruler now and hit the  paper so that it will get pulled out quickly. Does the coin come? 
  • Further Activities.

The experiment may be repeated in many other ways. Here are some suggestions.

  1. Use the same coin   , same paper but vary the force.
  2. Use the same coin, same force but vary the mat. [Instead of paper you may use cloth]
  3. Use the same paper, same force but different coins or other objects.

 Have you got a clue as to the behavior of the coin?

 If you push the paper quickly the coin stays but if you pull slowly giving a lower force the coin comes.

 

This can be explained by the Newton's Laws.

 According to the first law, all bodies are reluctant to change their state of motion. That means if a body is moving, it prefers to continue the motion or if stationery it will remain so until an unbalanced force acts on it.

 The reluctance of a body to change its state of motion is called "inertia".

 This explains why the coin does not move with the paper.

Yet the problem remains why the coin goes with the paper if pulled slowly?

 

Lily:- Isn't that simple. when the paper is pulled the under surface of the coin rubs on the paper. This creates a frictional force that makes the coin move.

Ali:- Well what is friction? This is a force which acts in the opposite direction to the movement of a body. The paper moves to right say. Then the friction must be in the opposite direction. The coin moves in the same direction as the paper.

 Who can answer this question? The best answer will be published here with your name.

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