A system of forces is shown in FIGURE 7.1 - NSC Mechanical Technology Welding and Metalwork - Question 7 - 2016 - Paper 1
Question 7
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.
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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°)≈1.99extkN
The horizontal component of the force at 2.1 kN is:
2.1extkN×extcos(40°)≈1.61extkN
Lastly, 4.7 kN is added directly as it is completely horizontal.
Thus, the overall horizontal resultant is:
RH=4.7+1.61−1.99≈4.32extkN
Step 2
Calculate the resultant of the vertical components.
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For the vertical components, we consolidate the vertical forces:
The component from the 2.1 kN force:
2.1extkN×extsin(40°)≈0.96extkN
From the 3.1 kN force:
3.1extkN×extsin(50°)≈2.37extkN
The overall vertical resultant then is:
RV=0.96+2.37≈3.33extkN
Step 3
Calculate the magnitude of the equilibrium force.
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Next, the magnitude of the equilibrium force can be determined using:
E=RH2+RV2
Substituting the values:
E=(4.32)2+(3.33)2≈5.43extkN
Step 4
Calculate the equilibrium angle with reference to the horizontal plane.
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The equilibrium angle can be computed with:
tan(θ)=RHRV
Calculating:
θ=tan−1(4.323.33)≈39.35°
Step 5
Stress Calculation in the Bolt Material.
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To calculate the stress in the bolt material, we first determine the force acting on the bolt:
F=m⋅g=600extkg⋅10extm/s2=6000extN
Next, the cross-sectional area for an M16 bolt is:
A=4πd2=4π(0.016)2≈2.01×10−4extm2
Stress is then given by:
Stress=AF=2.01×10−46000≈29.84extMPa
Step 6
Define Pascal as the unit for stress in a material.
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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: