Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Pulling Newspaper below the Tumbler

Introduction

This is another experiment which is very interesting, dramatic and eye catching and which is supposed to exhibit the ``inertia of rest''. Our extension to this experiment shows that the explanation is inadequate.

Apparatus

A glass tumbler, a strip of news paper

Procedure

  1. Place the glass tumbler on a table near its edge and mark the boundary with a piece of chalk. Remove the tumbler.
  2. Take the strip of newspaper, and spread it on the table. Put the tumbler on the strip near its edge. Mark the boundary with a pen. Match the two boundaries by shifting the strip. Let the remaining part of the strip hang over the edge of the table.
  3. Hold the hanging strip firmly with both your hands. The hanging part is tight and vertical at this stage.
  4. Pull the strip down with a sharp jerk. The whole strip will be in your hand and the tumbler will stand still on the table.

Check the position of the tumbler.

  • Question: Is the tumbler right in the boundary on the table, or it moved forward or backward?

Discussion

As the strip starts moving below the tumbler it exerts frictional force on the tumbler. Because of this, the tumbler moves ahead.