Application of Newton's Laws of motion

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Homework Help Overview

The discussion revolves around a problem involving Newton's Laws of motion, specifically focusing on a block being pushed against a vertical surface at an angle, with friction playing a critical role in determining the force required to keep the block stationary.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the force required to hold the block still, with one participant questioning the initial calculation and others exploring the relationship between the applied force and friction. There are attempts to formulate equations that incorporate gravitational and frictional forces.

Discussion Status

The discussion is active, with participants questioning the validity of equations presented and the assumptions made regarding the forces at play. Some guidance is offered regarding the dependence of friction on the applied force, but no consensus has been reached on the correct approach or solution.

Contextual Notes

Participants are navigating through the implications of the angle of application and the coefficient of friction, with some uncertainty regarding the correct formulation of the problem and the necessary equations to solve it.

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A block of mass 20kg is pushed against a vertical surface at an angle of 30 degrees as shown. The coefficient of friction between the surface and the block is 0.2. What is the minimum magitude of P to hold the block still?


I got 271.5 when I tried but the answer is 202.2
 

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How did you come to the 271.5?
 
Have you taken into account the fact that the frictional force will depend also on P, ie how strongly it is being pressed against the wall?
 
I came up withthe equation

mg+ Fr = mg cos theta
 
That equation does not look right. Where is P?

Also how do you determine Fr. You need another equation right?
 

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