Differences

This shows you the differences between two versions of the page.

--- 183_notes:friction [2021/02/18 21:20] – [The normal force] stumptyl
+++ 183_notes:friction [2021/02/18 21:22] – [Forces due to contact] stumptyl
@@ Line 3: / Line 3: @@
 ===== Contact Interactions: The Normal Force & Friction =====
-A microscopic perspective of materials helps to explain how contact interactions occur in nature. Contact interactions (forces) are not themselves [[http://en.wikipedia.org/wiki/Fundamental_interaction|fundamental forces of nature]], but they are the result of electrical forces between atoms. Compression and extension of materials occur not only at the [[183_notes:model_of_a_wire#modeling_the_solid_wire|macroscopic level]], but also at the [[183_notes:youngs_modulus#hanging_a_mass_from_a_platinum_wire|microscopic level]]. In these notes, you will read about how these ideas give rise to forces due to contact such as the [[http://en.wikipedia.org/wiki/Normal_force|normal force]] and dry [[http://en.wikipedia.org/wiki/Friction|friction]].
+A microscopic perspective of materials helps to explain how contact interactions occur in nature. Contact interactions (forces) are not themselves [[http://en.wikipedia.org/wiki/Fundamental_interaction|fundamental forces of nature]], but they are the result of electrical forces between atoms. Compression and extension of materials occur not only at the [[183_notes:model_of_a_wire#modeling_the_solid_wire|macroscopic level]], but also at the [[183_notes:youngs_modulus#hanging_a_mass_from_a_platinum_wire|microscopic level]]. **In these notes, you will read about how these ideas give rise to forces due to contact such as the [[http://en.wikipedia.org/wiki/Normal_force|normal force]] and dry [[http://en.wikipedia.org/wiki/Friction|friction]].**
 ===== Forces due to contact =====
-When two objects are in contact, their contact surfaces exert forces on each other. This is quite different from the gravitational force because while it acts on every piece of mass, as you will learn, we consider that it acts at the [[http://en.wikipedia.org/wiki/Center_of_mass|center of the of mass]] of the object. This assumption doesn't often affect our predictions and explanations of motion.  In fact, in all the models that you have used so far, we haven't been concerned about exactly where the force acts on an object only that it does act.
+When two objects are in contact, their contact surfaces exert forces on each other. This is quite different from the gravitational force because while it acts on every piece of mass, as you will learn,__ //_we consider that it acts at the [[http://en.wikipedia.org/wiki/Center_of_mass|center of the of mass]] of the object.//__ This assumption doesn't often affect our predictions and explanations of motion.  In fact, in all the models that you have used so far, we haven't been concerned about exactly where the force acts on an object only that it does act.
 For contact forces, (for a time) you will continue to use the assumption that we can just consider whether a contact force acts or not (And in what direction it acts). In the future, you might need to know precisely where it acts because [[183_notes:pp_vs_real|it might cause the motion to be a bit more complicated]]. For example, you can tip a box over if you push on it at the right location, but below that location it doesn't tip over.