Materials Needed:
- Plank of wood
- Ruler
- Sheets of materials
- Small objects made of various materials
- Lubricants: oil, graphite, soap, etc.
Procedure: (see Figure 12)
- Put the first sheet on the plank.
- Place the first object on this wheet/plank setup
- Tilt the plank until the object begins to slide
on the sheet - note the height with the ruler.
- Repeat this process with combinations of the
sheets and objects you have.
- Now repeat this process for all the object and
sheet combinations with different lubricants
noting the heights in the chart.
- Which combination of object and sheet had the
least amount of friction? (moved at the
lowest height)
Figure 12: Friction investigation setup
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To choose the best materials for axles and bearings find samples
of the different materials you may want to use and test the friction
between them.
Keep in mind that it can be difficult to un-lubricate something
if it doesn't work, so test a scrap piece of material using this
friction test before lubricating your car components if you are not
sure.
Observations:
The lower the friction, the sooner the object will start to slide
and the smaller the angle will be. One interesting feature of this
investigation is that the weight of the object is not important.
A steel paper clip will start sliding at the same angle as a heavy
steel object. Picking two materials that "run" well together will mean
that less power will be used to overcome the friction and more will go
towards driving the car faster.
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