Forces Investigations

Discuss the Forces in action in these pictures

rollers friction02
f1 burning rubber02
cycling w
mars heat shield02
elastic w
mag1 w
stretch1 w
magnet w
elect insulator images[1]
Tyne bridges

Scientists are interested in measuring and comparing Forces in all sorts of situations eg.

In fabrics used in sports and other clothing.

In materials which need to grip on different surfaces.

In magnetic materials which have all sorts of uses including cranes and medical scanners.

In structures which support heavy loads such as bridges or the stands in a stadium.

Science Investigations


1. How many times greater is the grip on one side of the block compared to the other?

2. Which type of floor covering is the safest for use in a bathroom or kitchen?


Which type of cloth (coloured elastic bands) is best for use in making cycling shorts?


Which pair of magnets is the strongest?


How strong is a paper tube?

How can forces be applied in classroom based investigations where measurements have to be made?

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.



Managing jars of marbles in the classroom!
The best and least expensive way to manage using the marbles is to have two types of container for each group of pupils. One plastic container with screwcap for storage and to count out from and a second plastic container to ‘count in’ the marbles in order to apply the force in the experiment. A plastic 1 pint or half litre milk carton is best because it is easy to attach a string to the handle which in turn can be hooked on using a simple paper clip. Also, if the carton falls to the ground it will not be damaged and only a few marbles if any will escape from the narrow mouth of the container! Actually it’s good, harmless fun to let the container crash to the ground in a strength test or magnetic strength experiment - it adds to the surprise and is a good illustration of the force of gravity!

It’s good to have some basic rules about marbles...

  1. Only one marble is allowed in the hand, the rest must be in the storage container or the ‘experiment’ container.
  2. Never pour the marbles out on the desk or into a lid etc.
22-5-12 023

This picture shows a simple way to test the strength of a paper roll tube and is an excellent simulation of the strength testing of a ‘beam’ used in a large structure or building.

The paper tube is suspended in a gap between two chairs or tables or boxes as shown.

A string loops around the tube and through the handle of the milk carton. Using a loop is better than a single string because the children tend to tie lots of knots!!! Using a loop with a single pre-tied knot you don’t need any further knots.

One marble at a time is added until the tube buckles and collapses. The carton hits the ground with a crash.

A bridge made from paper roll tubes can be tested in this way but you will need lots and lots of marbles!

In a similar way we can use marbles in all sorts of forces investigations.

eg. Friction
A long string is used to attach a friction block (see FRICTION investigation) on the desk to a milk carton hanging over the end of the desk in mid air. Marbles are added until the block slides and this is a measure of the frictional force between the block and the desk. This investigation can be extended to different materials such as floor coverings


This drawing was made by a year 5 pupil and shows a friction block made of wood but with a rubber sheet attached to one surface. It is being pulled along the desk by a cup with marbles in it. A simple investigation like this can tell us how many times greater the grip is on one side of the block compared to the other.

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