AIEEE 2006 Solved Paper

From work energy theorem we can say,
Work done by tension + work done by force (applied) + Work done by gravitational force = change in kinetic energy Here Work done by tension is zero
‌⇒0+F×AB−Mg×AC=0
⇒F=Mg(‌

AC

AB

)=Mg[‌

1− 1 √2

1 2

]
as AB=ℓsin‌45∘=‌

ℓ

√2

and AC=OC−OA=ℓ−ℓ‌cos‌45∘=ℓ(1−‌

1

√2

)
where ℓ= length of the string.
‌⇒F=Mg(√2−1)