Frictional Forces
Hook
Video: A World Without Friction. This video demonstrates the importance of frictional forces in our world and just how they impact our every day lives. Even though frictional forces are vital in our every day lives, cars and airplanes are engineered to reduce these forces to a minimum. This leads to fuel reductions and greener alternatives. Figure A7. Free body diagram 4 - A box experiences 1N of frictional force while being pulled with a force of 3.61N [E56.31°N] and another force of 6.08N [E9.46°N]. In what direction will the frictional force point towards and what is the direction and magnitude of the net force? ([W9.46°S]; 5.08N [E9.46°N])
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Pedagogical Approach
Static friction and kinetic friction need to be explained properly since many students become confused between the two. It is also very important to make it clear to students that the direction frictional forces is always opposite the motion of the object. So until the net force, not including friction, is determined in magnitude and direction, it is not possible to know in what direction frictional forces will point towards. |
Activity: Simulation on a flat surface This simulation allows for students to interact with frictional forces. They will be able to investigate the relationship between the static coefficient and the kinetic coefficient by playing with the amount of force needed to move a stationary object and the amount of force to keep a moving object from becoming static. This can also be turned into a lab for the students to do hands on. |
Activity: Simulation on an Inclined Plane This simulation is very similar to the one above except that it is done on an inclined plane. |
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Activity: Determining Coefficients of Static and Kinetic Friction. This is a lab that be used to deepen the understanding of static friction and kinetic friction. |
Consolidation
The main concepts that students should leave knowing about frictional force is that it always point opposite the direction in which the object is moving and that the static coefficient of friction is always less than the kinetic coefficient. Students need to understand the application of each coefficient. Below are examples of some exit slip. They can be used individually or combined. Exit slip: Which coefficient is always greater than the other . Explain why. Exit slip: In what direction do frictional forces always point towards? |
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