A mass of Mkg is suspended by a weightless string. The minimum horizontal force that is required to displace it slowly until the string makes an angle of 450 with the initial vertical direction is
A
Mg(√2+1)
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B
Mg√2
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C
Mg√2
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D
Mg(√2−1)
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Solution
The correct option is BMg(√2−1) Here, the constant horizontal force required to take the body from position 1 to position 2 can be calculated by using work energy theorem. It is given that body is taken slowly so that its speed doesn't change, then ΔK.E=0 =WF+WMg+Wtension [symbols have their usual meanings] WF=F×lsin450, WMg=Mg(l−lcos450),Wtension=0 F=Mg(√2−1)