## yrelhan4 3 years ago The end of uniform rope of mass 'M' and length 'L' that is piled on a platform is lifted with a constant velocity 'v' by a variable force F . Find the value of force 'F' as lifted postion of 'x' .

Hint: Start by using this definition of force. Force is the time rate of change of momentum i.e.$F=dP/dt=d(mv)/dt=vdm/dt+mdv/dt$ the mass the force is lifting is changing. the mass at any given instant is $m=\frac{ M }{ L }x$ where x is the length of rope lifted. We also know $x=vt$ substitute and solve.