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Newton's second law problem with friction

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1. The problem statement, all variables and given/known data

i did part a,b,c but i am confused about part d.. i have a test tomorrow and will reattempt this when i wake up but i really need a hint here..so when the worker pulls upward he is decreasing the magnitude of -mg right? so if Fn and mg initially cancel each other out, when the worker pulls upward he is making it so that the acceleration in the y direction is no longer 0 correct? so netforceydirection = Fn-mg+Fpull and it is non zero?


2. Relevant equations


3. The attempt at a solution
 

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i did part a,b,c but i am confused about part d.. i have a test tomorrow and will reattempt this when i wake up but i really need a hint here..so when the worker pulls upward he is decreasing the magnitude of -mg right? so if Fn and mg initially cancel each other out, when the worker pulls upward he is making it so that the acceleration in the y direction is no longer 0 correct? so netforceydirection = Fn-mg+Fpull and it is non zero?
the frictional force opposing the horizontal push is = coefficient of friction x R (the net reaction)
initially R= weight mg of the crate
after help say of F1 upward F1+ R = mg

so R= mg- F1 thereby reducing the frictional force = mux(mg-F1)
in the horizontal direction. so it will help him push easily
 

gneill

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You really need to use the homework template more effectively. What you've put in the problem statement belongs in the Attempt at solution section, and you should list any equations that you think are relevant to this type of problem in the Relevant equations section. See the pinned thread, Guidelines for students and helpers, for tips on how to create effective homework help requests.

An empty Attempt at solution section is a major flag to moderators to scrutinize your post to judge whether or not you've put any effort so far. Helpers, who are volunteering their expertise, shouldn't have to tease out your efforts from random places in the post.

Considering the points you've raised in your post, I am wondering whether or not you've drawn Free Body Diagrams for the scenarios. Have you done that?
 

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