Question

A body of mass w is suspended by a string. it is pulled a side with a horizontal force of 2w and held at rest, the tension in string is​

Answer 1

Answer:

By conservation of energy, work done by force = increase in potential energy.

From the figure we have:

⇒l=2Rsin(22.5°)

⇒W=Flcos(22.5°)

⇒W=FR(2sin(22.5°)cos(22.5°))=FRsin(45°)=

2

FR

Change in potential energy =Mgh=MgR(1−cos(45°))=MgR(1−

2

1

)

⇒MgR(1−

2

1

)=

2

FR

⇒F=Mg(

2

−1)