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

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In summary, the problem involves a 10m long, 400N uniform ladder leaning against a frictionless wall at a 30° angle with the horizontal. The ladder is also supported by a peg on the ground. The magnitude of the force exerted by the ladder on the peg is 470N, which is the sum of the horizontal force from the peg and the vertical force from the ladder's weight. There is no friction at the peg.
  • #1
Ishida52134
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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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  • #2
any ideas
 
  • #3
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.
 
  • #4
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
 
  • #5
Yeah, that's what I get. looks like a book error to me.
 

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

1. How do you calculate the force on a peg in a uniform ladder against a wall?

To calculate the force on a peg in a uniform ladder against a wall, you will need to use the principles of statics. This includes taking into account the weight of the ladder, the weight of the person on the ladder, and the angle of the ladder against the wall. Using the equation F = mg, you can calculate the force on the peg.

2. What is the importance of calculating the force on a peg in a uniform ladder against a wall?

Calculating the force on a peg in a uniform ladder against a wall is important because it allows for the determination of whether the ladder will remain in a stable position or not. This information is crucial for ensuring the safety of the person using the ladder and preventing accidents.

3. How does the angle of the ladder against the wall affect the force on the peg?

The angle of the ladder against the wall directly affects the force on the peg. As the angle increases, the force on the peg also increases. This is because the weight of the ladder and the person on it are distributed differently as the angle changes, resulting in a different force being applied to the peg.

4. What factors can influence the calculation of force on a peg in a uniform ladder against a wall?

Aside from the weight of the ladder and the person on it, other factors that can influence the calculation of force on a peg in a uniform ladder against a wall include the strength and stability of the wall, the condition of the ladder, and any external forces acting on the ladder (e.g. wind).

5. Are there any safety precautions to consider when calculating the force on a peg in a uniform ladder against a wall?

Yes, there are several safety precautions to consider when calculating the force on a peg in a uniform ladder against a wall. These include making sure the ladder is in good condition, using the correct ladder for the job, and having someone hold the ladder steady while it is being used. It is also important to double-check the calculations and ensure the ladder is properly secured against the wall before use.

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