Take a ball of string . Let one student from the class measure four hand spans of the string and cut it there . Let each of the other students in the class cut four hand-spans of the string , too . Now hold all the pieces together by one end . Are they all of the same length ?

Answer the following Questions: What would be the difference perceived between hearing only two pupils (students) in the class talking to each other and all the children taling to one another at the same time?

Take a long rubber band and cut it at one point . At one of its ends tie a clean washed stone or a 50g weight as shown in figure Now hold the other end of the rubber band and make a mark there . Keep the stone hanging in air and measure the length of the rubber band from the stone to the mark made earlier . now take water in a pot and hold the rubber band at such a height that the stone sinks in it . again measure the length of the rubber band up to the mark . : What is observed ?:

Take a long rubber band and cut it at one point . At one of its ends tie a clean washed stone or a 50g weight as shown in figure Now hold the other end of the rubber band and make a mark there . Keep the stone hanging in air and measure the length of the rubber band from the stone to the mark made earlier . now take water in a pot and hold the rubber band at such a height that the stone sinks in it . again measure the length of the rubber band up to the mark . : What could be the reason for a shorter length of the rubber band in water ? :