Media
In a tug-of-war between 3 WWE superstars and a lion, who do you think will win? Why? Draw a free body diagram to help defend your argument.
Lion vs WWE superstars in a tug of war (0:20)
Tug of war can be incredibly dangerous because there can be an incredibly large amount of tension in the rope. When the rope breaks, it snaps violently back towards the contestants.
Wikipedia – Tug of War – Notable Incidents
When walking on ice, there is not much friction, but the normal force is not affected. In the following videos, note how the robot/human/dog can not exert large horizontal forces with their feet, but can exert large vertical forces.
Boston Robotics – BigDog Overview (3:24 – watch from 0:35 to 2:23)
Dog Playing Fetch on Ice Rink Before NHL Hockey Game (0:51)
Dog on Slippery Ice (0:14)
Flow Drilling – Friction Drill (watch first 1:34 only)
ABS : how anti-lock braking system works in wet situations (0:50)
Why do ABS brakes cause the car to stop more quickly than non-ABS brakes?
In the following video, note how it is much harder for the dog to start moving the sled than it is to keep the sled in motion. This is because the static coefficient of friction is larger than the dynamic coefficient of friction.
L’Appel de la Foret is based on the short novel Call of the Wild by Jack London.
L’appel de la forêt (1:40:08 – watch from 1:25:46 to 1:27:52)
In reality, the coefficient of friction follows a Stribeck curve.
Skiing on rails (and boxes) is difficult because the coefficient of kinetic friction between skis and the rail is very close to zero. This means that your feet must be almost directly under your body to keep from falling over. This feels very unnatural, as this posture would cause you to fall over if you attempted it on snow.
Skiing Rail Grind Fail (0:11)
Ski Rail Slide to Back Slam Fail (0:13)
Kid Fail When Try To Rail (0:02)
https://www.youtube.com/watch?v=XJCcQgCrjkQ
Skiing the World’s Longest Rail | Jesper Tjäder (9:16 – watch from 7:35 to the end)
GoPro: Jesper Tjäder`s Loop from Supervention II (2:28 – watch from 1:35 to 2:12)
Activities and Worksheets
Amrita University – Friction Lab (3:27)
This lab is very similar to the research that Leonardo da Vinci did on tribology.
Worksheet Solutions – Friction