1.5 m long cord AB can withstand a maximum 4


If the 1.5 m long cord AB can withstand a maximum force of 3500 N, determine the force in cord BC and the distance y so that the 200-kg crate can be supported.

1.5 m long cord AB can withstand a maximum

Image from: Hibbeler, R. C., S. C. Fan, Kai Beng. Yap, and Peter Schiavone. Statics: Mechanics for Engineers. Singapore: Pearson, 2013.

Solution:

Show me the final answers↓
Let us draw a free body diagram focusing on ring B.

1.5 m long cord AB can withstand a maximum

First, we will write an equation of equilibrium for y-axis forces as this will allow us to figure out a value for θ.

+\uparrow \sum \text{F}_\text{y}\,=\,0

3500\text{sin}\,(\theta)\,-\,1962\,=\,0

\text{sin}\,(\theta)\,=\,\dfrac{1962}{3500}

(solve for \theta)

\theta\,=\,\text{sin}^{-1}\left(\dfrac{1962}{3500}\right)

\theta\,=\,34.1^0

 

Let us now write an equation of equilibrium for x-axis forces.

\rightarrow ^+\sum \text{F}_\text{x}\,=\,0

3500\text{cos}\,(34.1^0)\,-\,F_{BC}\,=\,0

(Solve for F_{BC})

F_{BC}\,=\,2898.2 N

Show me the free body diagram

 

We can now figure out the value of y by using trigonometry.

\text{sin}\,(34.1^0)\,=\,\dfrac{y}{1.5}

y\,=\,1.5\,\text{sin}\,(34.1^0)

y\,=\,0.84 m

 

Final Answers:

F_{BC}\,=\,2898.2 N

Length of y = 0.84 m

 

This question can be found in Engineering Mechanics: Statics (SI edition), 13th edition, chapter 3, question 3-25.

 


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4 thoughts on “1.5 m long cord AB can withstand a maximum

  • Johan

    Hi Question Solutions! I am hoping you could help me!

    I’m struggling to understand this question. If Hibbeler said

    “The tension in the cord BA (i.e. T_BA) is 3500 N. Calculate the force in cord BC and the distance y.”.

    then I would understand this question.

    However, Hibbeler wrote “If the 1.5 m long cord AB can withstand a maximum force of 3500 N…”.

    Doesn’t this imply that the tension in the cord BA is at most 3500 N. Mathematically, this would be written as T_BA ≤ 3500.

    However, to calculate the answers to this question, we have to assume T_BA = 3500. Why do we do this?

    Thank you for your help.

    • questionsolutions Post author

      So you actually said the answer in your own question. You wrote T_BA ≤ 3500, which in simple words means “TBA can be equal to 3500 or less than 3500.” So we use the maximum ceiling value of 3500.