A beam AB has mass 12 kg and length 5 m - Edexcel - A-Level Maths Mechanics - Question 5 - 2008 - Paper 1
Question 5
A beam AB has mass 12 kg and length 5 m. It is held in equilibrium in a horizontal position by two vertical ropes attached to the beam. One rope is attached to A, th... show full transcript
Worked Solution & Example Answer:A beam AB has mass 12 kg and length 5 m - Edexcel - A-Level Maths Mechanics - Question 5 - 2008 - Paper 1
Step 1
Find (i) the tension in the rope at C
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Answer
To find the tension in the rope at C, we can use the principle of moments about point A.
The weight of the beam (W_beam) is given by:
Wbeam=mg=12imes9.81=117.72extN
Taking moments about A:
TCimes4=Wbeamimes2.5
Substituting the weight of the beam:
TCimes4=117.72imes2.5TC=4117.72imes2.5=73.575extN
Thus, the tension in the rope at C is approximately 73.6 N.
Step 2
Find (ii) the tension in the rope at A
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Answer
Using the equilibrium condition for vertical forces, we have:
TA+TC=Wbeam
Substituting the values:
TA+73.575=117.72TA=117.72−73.575=44.145extN
Thus, the tension in the rope at A is approximately 44.1 N.
Step 3
Find (b) in terms of y, an expression for the tension in the rope at C
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Answer
Considering the additional load of mass 16 kg at a distance y from A, we can express the new tension in the rope at C. The total weight (W_load) of the additional load is:
Wload=16imes9.81=156.96extN
Taking moments about point A again:
TCimes4=Wbeamimes2.5+Wloadimesy
Substituting:
TCimes4=117.72imes2.5+156.96imesy
Solving for T_C gives:
TC=4117.72imes2.5+156.96y
Step 4
Find (c) the range of possible positions for the load
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Answer
To ensure the rope at C does not break, we need:
TC≤98extN
Substituting our expression for T_C:
4117.72imes2.5+156.96y≤98
Multiplying through by 4 results in:
117.72imes2.5+156.96y≤392
Calculating the left side:
294.3+156.96y≤392
Rearranging gives:
y \leq \frac{97.7}{156.96}\
y \leq 0.6226 ext{ m}$$
Thus, the load must be no more than 0.6226 m from A.