Objective :

To discuss misconconcets about Inertia  

Introduction :

Newton’s three law of motion are taught in school from quite early times. Though students know the statements of the three laws but when it comes to application, quite often the laws are wrongly interpreted. The experiment described is quite common and is shown to dramatize the concept of Newton’s 1st law of motion or inertia. However, a detailed analysis reveals greater insight into the laws.

Keywords :

Inertia, Newton's laws.

Equipment :

A glass tumbler, a long piece of paper, a table.   


Near the edge of a table, place a glass tumbler filled with water. Now hold the part of the paper overhanging from the table using both hands. Give a sharp jerk to the paper and pull it quickly.

What you find is that the paper comes out from below the glass and the glass just stays on the table with no water spilling out.

Try pulling the paper with different speeds and see what happens.

Discussion :

The common explanation is that because of inertia, the glass remains at its place and the paper comes. But is it the explanation? Where does this inertia go, when the paper is pulled slowly? Does inertia depend on velocity?

It is friction, acceleration and distance moved under this acceleration that have to be roped in for proper understanding

Hazard :

If you are using glass tumber and dont pull it quickly it may fall. Use steel glass to practice.