Jump to content
JohnATL

Dynamics supplement question 19

Recommended Posts

On problem 19(c) of the supplemental questions for AP1 Dynamics I must be doing something wrong with the Trig functions to solve for the tension in each wire, but the problem is not worked out in the answer, it simply says to substitute the appropriate trig functions to solve.  Can someone show me the steps for that so I achieve the correct answer?

Thanks!

 

 

AP1 Dynamics 19.pdf

Share this post


Link to post
Share on other sites

Thank you!  While waiting for your answer I discovered another shortcut that is a bit quicker, but only works when the two angles equal 90°.  Simply take the sin of each angle and multiply them times mg to get T1 and T2.  I think your solution is universal however, even if the angles don't add up to 90°.  How often do AP1 questions include this type of question where the angles don't sum up to 90°?

59d25eb4f0173_ScreenShot2017-09-30at9_09_12PM.jpg.2b9e9520116e2426aaa45431e4d0d083.jpg

Share this post


Link to post
Share on other sites

This is a very common type of question, and the process of breaking up forces on a FBD into components and applying Newton's 2nd Law carries throughout the entire course.  One of those things you've gotta learn.  :angel:   The "shortcut" that you learned isn't really a shortcut, and isn't something I'd recommend, as it won't carry through to other situations in which the third force isn't caused by gravity on a mass.  I'd focus on learning how to draw free body diagrams, break forces at angles into components, and applying Newton's 2nd Law.  It's the backbone of mechanics, and very important in further units as well.  Good luck!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


Terms of Use

The pages of APlusPhysics.com, Physics in Action podcasts, and other online media at this site are made available as a service to physics students, instructors, and others. Their use is encouraged and is free of charge. Teachers who wish to use materials either in a classroom demonstration format or as part of an interactive activity/lesson are granted permission (and encouraged) to do so. Linking to information on this site is allowed and encouraged, but content from APlusPhysics may not be made available elsewhere on the Internet without the author's written permission.

Copyright Notice

APlusPhysics.com, Silly Beagle Productions and Physics In Action materials are copyright protected and the author restricts their use to online usage through a live internet connection. Any downloading of files to other storage devices (hard drives, web servers, school servers, CDs, etc.) with the exception of Physics In Action podcast episodes is prohibited. The use of images, text and animations in other projects (including non-profit endeavors) is also prohibited. Requests for permission to use such material on other projects may be submitted in writing to info@aplusphysics.com. Licensing of the content of APlusPhysics.com for other uses may be considered in the future.

×