A uniform meter rule AB is balanced on a knife edge placed 58cm from A when a mass of 20.0Kg is placed 25cm from B. Calculate the mass of the rule and the force exerted on the rule by the knife edge
"AB = 1m"
"g= 9.8\\frac{m}{s^2}"
"\\text{let }K\\text{-point where the knife is located}"
"AK = 58cm = 0.58m"
"BK = AB-AK = 0.42m"
"\\text{let }M\\text{-point where the mass is located }m_1=20kg"
"BM =25cm = 0.25m"
"KM = BK-BM= 0.18m"
"\\text{let point } O \\text{ midpoint of the ruler}"
"m - \\text{this is the mass of the ruler}"
"AO = \\frac{AB}{2}=0.5m"
"KO = AK-AO = 0.08m"
"KO*mg=KM*m_1g"
"m= \\frac{KM*m_1}{KO}=\\frac{0.18*20}{0.08}=45kg"
"N = mg+m_1g= 637N"
"\\text{Answer: }"
"\\text{the mass of the rule }45kg"
"\\text{the force exerted on the rule by the knife edge }637N"
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