Calculating Force on Peg in Uniform Ladder Against Wall | Quick Statics Question

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Homework Help Overview

The problem involves a uniform ladder resting against a frictionless wall, with a peg preventing it from slipping. The ladder's length, weight, and angle with the horizontal are specified, and participants are tasked with calculating the force exerted on the peg by the ladder.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss identifying forces acting on the ladder, including normal force, weight, and forces from the wall and peg. There is an attempt to calculate moments about the base of the ladder, leading to questions about the role of friction and the relationship between the forces at play.

Discussion Status

Some guidance has been offered regarding the absence of friction at the peg and the need to calculate both horizontal and vertical forces. However, discrepancies in calculated values and answer choices have led to uncertainty, with some participants suggesting a possible error in the source material.

Contextual Notes

Participants are working under the constraints of the problem's parameters and the provided answer choices, which may not align with their calculations. The discussion reflects a mix of interpretations regarding the forces involved.

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Homework Statement


A uniform ladder is 10m long and weighs 400 N. It rests with its upper end against a frictionless
vertical wall. Its lower end rests on the ground and is prevented from slipping by a peg driven
into the ground. The ladder makes a 30◦ angle with the horizontal. The magnitude of the
force exerted on the peg by the ladder is:

A. zero
B. 200N
C. 400N
D. 470N
E. 670N


Homework Equations


torque = r x F




The Attempt at a Solution


First I identified the forces. So normal force, frictional force, weight, and force from the wall and force from the peg which acts horizantally.
Basically, I just took moments about the base of the ladder. I got -400(5cos30) + 5Fw = 0.
Then I solved for Fw getting 346.
Then I set all x forces equal to each other. Getting 346 = Fpeg + Ffrictional.
And I got stuck lol.

I don't know if there's no frictional force at all and that the peg is acting in place of it or if it's the sum of them together that provides the x component.
 
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any ideas
 
There is no friction at the peg. So calculate the horizontal force that the peg exerts on the ladder. Don't forget the vertical force also.
 
oh thanks.
But I keep getting 529 as the magnitude which isn't any of the answer choices. And the answer is supposed to be 470N
 
Yeah, that's what I get. looks like a book error to me.
 

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