Introductory Static Friction on an Incline Problem

A book is resting on a board. One end of the board is slowly raised. The book starts to slide when the incline angle is 15°. What is the coefficient of static friction between the book and the incline?

0:00 The example
0:44 Drawing the free body diagram
1:41 Net force in the parallel direction
2:11 Demonstrating why the acceleration in the parallel direction is zero
3:58 Force normal does not equal force of gravity
4:32 Net force in the perpendicular direction
5:07 Return to the parallel direction
6:06 Substituting in numbers

You can use the "Measure" App in iOS to measure an incline angle like this.

Next Video: Calculating the Uncertainty of the Coefficient of Friction

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Previous Video: Physics "Magic Trick" on an Incline

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[stephanburnett]

hey, this really helped with my physics lab thanks, your way of explaining things are very cool!!

[richardfeynman]

I have been teaching physics on the high school and college levels for 38 years. You're good!

[artinacart]

This is great! Well explained, silly, fun. This channel deserves some more recognition

[AustinoDLG]

Awesome video! My college physics class was stumping me (especially with friction).

[hectichive]

Thanks for the video! Really helping me with my physics homework! I had a question where I was trying to figure out the maximum angle a driveway could be above the x-axis before it started to roll down given a coefficient of static friction = 0.94. And I figured it out! I'm so happy rn, AP Physics is actually destroying me.

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[LiFELoG-fq]

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[teresafielm]

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[mattt]

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[yami.jx]

"got it in my notes.. somewhere" LOL he never takes notes!

[neilopfer]

Very well done!! Wish I would have had this type of explanation back in the 1970s when I was taking physics as an undergrad.

[simranr.]

how did you keep your phone up while moving the ramp?

[Jason-kejf]

Your vids help me so much. Thanks, man

[meghna]

Wow such a great video! Thank you so much :)

[MrBerlington]

what would the dependent variable be in this experiment?

[chanakyasinha]

Bro i just wanna say.. I got one my type of physics understanding guy, its you 😎.. I love discussing quantum Mechanics and wants to go in every detail to unify macro level physics to micro.

[PhatzKitchen]

Hi. Your videos are excellent! Do you have anymore videos where you use phone apps to assist in simple experiments like these? I want my students to begin using their cellphones to learn science.

[alexandrat]

I have a question. Would changing the mass of the object affect the critical angle?