Overhead electricity cables for railway lines are supported by structures like the one shown - Edexcel - A-Level Physics - Question 14 - 2023 - Paper 1
Question 14
Overhead electricity cables for railway lines are supported by structures like the one shown.
An electric cable of mass 45 kg is suspended from a support rod X. A s... show full transcript
Worked Solution & Example Answer:Overhead electricity cables for railway lines are supported by structures like the one shown - Edexcel - A-Level Physics - Question 14 - 2023 - Paper 1
Step 1
Determine the forces and distances
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Answer
Let the weight of the cable be calculated first:
Weight (W) = mass × g = 45 kg × 9.8 m/s² = 441 N.
Next, identify the distance from the pivot point (the point where rod X meets the column) to where the force is applied. Here, the distance from X to the center of the cable is 1.5 m, and the angle θ = 35°.
Step 2
Set up the moment equation
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Answer
Taking moments about point X, we consider the clockwise moments due to the weight of the cable and the counterclockwise moment due to the force from rod Y (let's denote it as F_Y).
The moment due to the weight of the cable:
Moment_W = W * distance = 441 N * 1.5 m * cos(35°).
The moment due to the force from rod Y:
Moment_Y = F_Y * 1.3 m.
Step 3
Equate the moments
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Answer
Setting the clockwise moments equal to the counterclockwise moments:
441imes1.5imesextcos(35°)=FYimes1.3
From this equation, we can solve for F_Y.
Step 4
Solve for F_Y
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