Outcomes

Pupils can identify the force, pivot and perpendicular distance to the pivot for a range of machines/tools and are able to calculate the moment in Nm.
Pupils understand how the force and distance are related to the moment. They will investigate the relationships by altering the force and measure distnce for a range of masses on a balanced system.
Pupils are to understand the practical applications of changing the force and perpendicular distance for tools.
Pupils can find the centre of gravity for a lamina using a pin and plumbline.
Pupils can label the centre of gravity for a range of objects and can appreciate that it may not be located on the object itself.
Pupils investigate and can apply the principle of moments for a balanced object.
Pupils investigate how the upward forces on a light beam varies witht he position of a heavy object placed on the beam.

Specification References

1.23 recall and use the relationship between the moment of a force and its distance from the pivot: moment = force x perpendicular distance from the pivot
1.24 recall that the weight of a body acts through its centre of gravity

Using a large lever vary the distance to the pivot and use a forcemeter and pulley system to lift a pupil. From a range of readings get the student to predict how both the effort and perpendicular distance to the pivot is related to the moment or turning effect.

File too large to upload - laminated copies are provided with the circus- copy in science

Group the class into 5 groups of increasing ability. There are three Moment problems of varing difficulty. 1) 2) To find the mass of a retort stand using the principle of moments and 3) to find the centre of mass of a student.
Have two groups attempt activity 1, another two groups attempt activity 2 and one group will be challenged by activity 3. All three activities have cards explaining what they need to do and also have a 'hint' card to help groups who are stuggling.
They should be asked to read through the card and have a look at the equipment. They should then discuss the activity as a group and then go onto try

Class set of rulers and masses for principle of moments
Class set of rulers suspended from forcemeters, masses to hang, 1/2 meter rule
Class set of card, scissors, retort stand, cork and pin, sting and plastecine.
Set of 6 different tools with a 'force vector' labelled (made out of laminated paper with the 'effort' labelled.

A tank with water in it will be heavy and so is only to be moved by the technician; please refer to the Manual handling section of the Laboratory Lessons Health and Safety Risk Assessment
When using springs goggles must be worn
The main risk is from the vacuum pump and apparatus. The specific risk assessment must be read before using the apparatus.
General Laboratory Health and Safety Risk Assessment