Static friction preventing block from sliding

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Homework Help Overview

The discussion revolves around a physics problem involving static friction and forces acting on a block on an incline. The problem specifies a coefficient of static friction and asks for the minimum force required to prevent the block from sliding down the incline, given the mass of the block and the angle of the incline.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the forces acting on the block, including gravitational force and frictional force. There are attempts to establish the relationship between these forces and the conditions required for the block to remain stationary on the incline. Questions arise about how to set up the equations correctly to reflect the balance of forces.

Discussion Status

Some participants have provided partial equations and insights into the forces involved, while others seek clarification on how to properly equate these forces. There is an ongoing exploration of the conditions necessary for static equilibrium, but no consensus has been reached on the final formulation.

Contextual Notes

Participants note the importance of drawing a diagram to visualize the forces and mention the need to consider the coordinate system aligned with the incline. There is a sense of urgency as one participant indicates they are preparing for a test.

malta
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Homework Statement



If the coefficient os static friction between the incline and block is .3, then what is the minimum force,F, needed to prevent the block from sliding?
m=20kg theta= 50 degrees

Homework Equations



Normal force= mgcosx
Fs= uk mgcosx

The Attempt at a Solution



I know how to solve this this for the perpendicular force (up the ramp) but I can't seem to figure out how to do it for thr parallel force.
 
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malta said:

Homework Statement



If the coefficient os static friction between the incline and block is .3, then what is the minimum force,F, needed to prevent the block from sliding?
m=20kg theta= 50 degrees

Homework Equations



Normal force= mgcosx
Fs= uk mgcosx

The Attempt at a Solution



I know how to solve this this for the perpendicular force (up the ramp) but I can't seem to figure out how to do it for thr parallel force.

I assume that you drew yourself a diagram with a coordinate system that has its x-axis parallel to the inclined plane and its y-axis perpendicular to the plane. Then, what is the force due to gravity acting to move the block down the plane? What is the frictional force acting to oppose the motion down the plane? What is the condition on the sum of all forces along the plane so that the block does not move?
 
Fore due to gravity is mgsinx and the frictional force = (coefficient of fiction)(mgCosx)
And the condition on all forces along the plane so that the block doesn't move has to equal to zero

But I can't seem to get what to set equal to what
 
Last edited:
anyone? I am doing a test review for a test tomorrow so this would greatly help me
 
malta said:
Fore due to gravity is mgsinx and the frictional force = (coefficient of fiction)(mgCosx)
And the condition on all forces along the plane so that the block doesn't move has to equal to zero

But I can't seem to get what to set equal to what

You have the right parts.

Draw a diagram and add the forces that need to make it be static.
 
ok so
F + mgcosx= N
(friction)N= mgSinx

So F = (mgSinx)/(friction) - mgCosx

There we go, thanks again
 
malta said:
ok so
F + mgcosx= N
(friction)N= mgSinx

So F = (mgSinx)/(friction) - mgCosx

There we go, thanks again

Not exactly.

F + μmgcosθ = mgsinθ

You only need to supply force in excess of what friction alone will not.
 

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