All of these investigations require a FORCE in order to make something happen eg. A force to make a wooden block slide along the desk in a friction experiment or a force to stretch a sample of cloth or elastic band.
It is common to use a FORCE-METER to apply and measure a force but there are simpler ways which require less expensive kit! Force-meters have their drawbacks too! - they are cumbersome to use because they are too long eg. in an experiment where something hangs over the end of the desk! The desk is acting as a support structure because tall metal stands are not always available.
Force-meters are difficult to use in friction experiments where an object is pulled along because the reading changes far too erratically for a child to read!
What about ‘gramme masses’ eg. 10g, 100g etc?
These can be expensive and lots would be needed for a whole-class activity. They are excellent though, and allow for very accurate measurements.
A simple and very effective alternative is a good old jar of marbles!
Marbles are easy to count out and are a great way to introduce the ‘fair test’ concept (eg. by deliberately introducing different sized marbles at a later stage in an experiment).
Marbles can easily be weighed too, so they can provide more precise results if required.
Using marbles it is possible to obtain excellent results which can be used to draw line graphs eg. for a stretching experiment on cloth strips, elastic bands or springs.