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A system of forces is shown in FIGURE 7.1 - NSC Mechanical Technology Welding and Metalwork - Question 7 - 2016 - Paper 1

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A system of forces is shown in FIGURE 7.1. Determine, by means of calculations, the magnitude and direction of the resultant for the system of forces in FIGURE 7.1. ... show full transcript

Worked Solution & Example Answer:A system of forces is shown in FIGURE 7.1 - NSC Mechanical Technology Welding and Metalwork - Question 7 - 2016 - Paper 1

Step 1

Calculate the resultant of the horizontal components.

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Answer

To find the resultant of the horizontal components, we summarize the horizontal forces:

  • The horizontal component of the force at 3.1 kN is calculated as:

3.1extkNimesextcos(50°)1.99extkN3.1 ext{ kN} imes ext{cos}(50°) \approx 1.99 ext{ kN}

  • The horizontal component of the force at 2.1 kN is:

2.1extkN×extcos(40°)1.61extkN2.1 ext{ kN} \times ext{cos}(40°) \approx 1.61 ext{ kN}

  • Lastly, 4.7 kN is added directly as it is completely horizontal.

Thus, the overall horizontal resultant is:

RH=4.7+1.611.994.32extkNR_H = 4.7 + 1.61 - 1.99 \approx 4.32 ext{ kN}

Step 2

Calculate the resultant of the vertical components.

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Answer

For the vertical components, we consolidate the vertical forces:

  • The component from the 2.1 kN force:

2.1extkN×extsin(40°)0.96extkN2.1 ext{ kN} \times ext{sin}(40°) \approx 0.96 ext{ kN}

  • From the 3.1 kN force:

3.1extkN×extsin(50°)2.37extkN3.1 ext{ kN} \times ext{sin}(50°) \approx 2.37 ext{ kN}

The overall vertical resultant then is:

RV=0.96+2.373.33extkNR_V = 0.96 + 2.37 \approx 3.33 ext{ kN}

Step 3

Calculate the magnitude of the equilibrium force.

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Answer

Next, the magnitude of the equilibrium force can be determined using:

E=RH2+RV2E = \sqrt{R_H^2 + R_V^2}

Substituting the values:

E=(4.32)2+(3.33)25.43extkNE = \sqrt{(4.32)^2 + (3.33)^2} \approx 5.43 ext{ kN}

Step 4

Calculate the equilibrium angle with reference to the horizontal plane.

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Answer

The equilibrium angle can be computed with:

tan(θ)=RVRH\tan(\theta) = \frac{R_V}{R_H}

Calculating:

θ=tan1(3.334.32)39.35°\theta = \tan^{-1}\left(\frac{3.33}{4.32}\right) \approx 39.35°

Step 5

Stress Calculation in the Bolt Material.

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Answer

To calculate the stress in the bolt material, we first determine the force acting on the bolt:

F=mg=600extkg10extm/s2=6000extNF = m \cdot g = 600 ext{ kg} \cdot 10 ext{ m/s}^2 = 6000 ext{ N}

Next, the cross-sectional area for an M16 bolt is:

A=πd24=π(0.016)242.01×104extm2A = \frac{\pi d^2}{4} = \frac{\pi (0.016)^2}{4} \approx 2.01 \times 10^{-4} ext{ m}^2

Stress is then given by:

Stress=FA=60002.01×10429.84extMPa\text{Stress} = \frac{F}{A} = \frac{6000}{2.01 \times 10^{-4}} \approx 29.84 ext{ MPa}

Step 6

Define Pascal as the unit for stress in a material.

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Answer

One Pascal (Pa) is defined as one Newton force (1 N) acting on an area of one square meter (1 m²). Thus, it is expressed as:

1extPa=1Nm21 ext{ Pa} = 1 \frac{N}{m^2}

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