A mass of M kg is suspended by a weightless string. The horizontal force that is required to displace it until the string makes an angle of 450 with the initial vertical direction is

The situation is shown in fig. (9)The constant force F required to take the body from position 1 to position 2 can be calculated by applying work-energy theorem. We assume that the body is taken slowly so that its speed doesn't change, i.e.ΔK=0WF+WMg+Wtension =0 Hero  WF=F×lsin⁡45∘ WMg=Mgl−lcos⁡45∘ Wtension =0 F×lsin⁡45∘+Mgl−lcos⁡45∘=0 or F=Mg(2−1)