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Example Nor/der 201398

The end of a string is fixed to a point [tex]\(A\)[/tex] on a vertical wall, and the other end is fastened to an object of weight [tex]\(8 \, \text{N}\)[/tex]. The object is pulled aside by a horizontal force, [tex]\(P\)[/tex], until the string is inclined at [tex]\(30^{\circ}\)[/tex] to the vertical. Calculate, correct to two decimal places, the:

a) Tension in the string
b) Horizontal force, [tex]\(P\)[/tex]


Sagot :

Sure, let's break down the steps to solve this problem. We have a string fastened to an object weighing [tex]\( 8 \text{ units} \)[/tex]. When pulled by a horizontal force [tex]\( P \)[/tex], the string makes an angle of [tex]\( 30^{\circ} \)[/tex] with the vertical wall.

a) Tension in the string ( [tex]\( T \)[/tex] ):

1. Identify the vertical and horizontal components:

- The weight of the object acts vertically downward and has a magnitude of [tex]\( 8 \text{ units} \)[/tex].
- The tension [tex]\( T \)[/tex] in the string has both vertical and horizontal components because the string is inclined.

2. Determine the vertical component of the tension:

Since the string makes an angle of [tex]\( 30^{\circ} \)[/tex] with the vertical, the vertical component of the tension in the string is given by [tex]\( T \cos(30^{\circ}) \)[/tex].

The vertical component of this tension must balance the weight of the object:
[tex]\[ T \cos(30^{\circ}) = 8 \][/tex]

3. Solve for the tension [tex]\( T \)[/tex]:

Knowing that [tex]\( \cos(30^{\circ}) = \frac{\sqrt{3}}{2} \)[/tex], we can rewrite the equation:
[tex]\[ T \frac{\sqrt{3}}{2} = 8 \][/tex]
Solving for [tex]\( T \)[/tex], we get:
[tex]\[ T = \frac{8}{\frac{\sqrt{3}}{2}} = \frac{8 \times 2}{\sqrt{3}} = \frac{16}{\sqrt{3}} \][/tex]

4. Simplify and round off the result:

Dividing and rationalizing the denominator is not necessary here, but rounding to two decimal places:
[tex]\[ T \approx 9.24 \][/tex]

So, the tension in the string, [tex]\( T \)[/tex], is approximately [tex]\( 9.24 \)[/tex] units.

b) Horizontal force ( [tex]\( P \)[/tex] ):

1. Determine the horizontal component of the tension:

The horizontal component of [tex]\( T \)[/tex] is given by [tex]\( T \sin(30^{\circ}) \)[/tex].

2. Solve for the horizontal force [tex]\( P \)[/tex]:

Since [tex]\( \sin(30^{\circ}) = \frac{1}{2} \)[/tex],
[tex]\[ P = T \sin(30^{\circ}) = T \times \frac{1}{2} \][/tex]

3. Substitute the value of [tex]\( T \)[/tex]:

Using [tex]\( T \approx 9.24 \)[/tex], we find:
[tex]\[ P \approx 9.24 \times \frac{1}{2} = 4.62 \][/tex]

So, the horizontal force, [tex]\( P \)[/tex], is approximately [tex]\( 4.62 \)[/tex] units.

Summary:
- Tension in the string ( [tex]\( T \)[/tex] ): [tex]\( 9.24 \)[/tex]
- Horizontal force ( [tex]\( P \)[/tex] ): [tex]\( 4.62 \)[/tex]

Both values are correct to two decimal places.
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