A metre stick, suspended from its mid-point, has a weight of 1.8 N hanging from the 20 cm mark - Junior Cycle Science - Question f - 2015
Question f
A metre stick, suspended from its mid-point, has a weight of 1.8 N hanging from the 20 cm mark. Calculate where a student must hang a weight of 2.7 N so that the met... show full transcript
Worked Solution & Example Answer:A metre stick, suspended from its mid-point, has a weight of 1.8 N hanging from the 20 cm mark - Junior Cycle Science - Question f - 2015
Step 1
Calculate the moment due to the 1.8 N weight
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Answer
To find the moment caused by the 1.8 N weight, we use the formula:
extMoment=extforceimesextdistance
Here, the force is 1.8 N and the distance from the pivot (the midpoint at 50 cm) is 50 - 20 = 30 cm. Therefore:
extMoment1.8N=1.8imes30=54extNm
Step 2
Calculate the distance for the 2.7 N weight to balance
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Answer
For the stick to be balanced, the moment from the 2.7 N weight must equal the moment caused by the 1.8 N weight:
54=2.7imesextdistance
Rearranging gives:
ext{distance} = rac{54}{2.7} = 20 ext{ cm}
Step 3
Determine the position to hang the 2.7 N weight
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Answer
To find where to hang the 2.7 N weight, we need to add the distance calculated to the pivot point:
extPosition=50extcm+20extcm=70extcm
Thus, the student must hang the weight at the 70 cm mark.
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