27404 Parallax Inc, 27404 Datasheet - Page 33

• Manufacturer Part Number: 27404
• Description: COMPETITION RING FOR SUMOBOT
• Manufacturer: Parallax Inc

Specifications of 27404

• Accessory Type: Hobby and Education
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: SumoBot®
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

To appreciate how different the coefficients of friction can be for different pairs of
materials, take a look at Table 1-2.
Figure 1-10 shows a graph you may have seen or will likely see in a physics book at
some point. The left side of the graph shows how the frictional force responds to the
applied force while the object is at rest. As more force (F) is applied, the frictional
opposing force increases by the same amount. When the applied force is more than the
product of the coefficient of friction and the normal force, the object will start to slide.
Once the object is sliding, the left side of the graph no longer applies. Since kinetic
forces are now at work, the right side of the graph explains what happens next. The
applied force can continue to increase, but all it does is increase the object's acceleration.
Reason being, force of kinetic friction resisting the applied force just doesn't get larger
than µ
calculated using F = m×a.
k
×N. Any force that exceeds this value contributes to acceleration, which can be
Strategy Consideration: The coefficient for each pair of materials is different. Let's say
your class will have a contest on a painted wood ring, but you are using the SumoBot
Competition Ring poster for practice. The tread material with the highest friction on the
poster isn't necessarily the material with the highest friction on the painted surface. If you
get the chance, test your collection of tread materials on the contest ring in advance.
Table 1-2: Examples of Coefficients of Friction
Rubber on Concrete
Copper on steel
Materials
Ice on ice
Chapter 1: Mechanical Adjustments · Page 29
0.53
1.0
0.1
µ
S
[3]
0.003
0.36
0.8
µ
K