Answer:
We must duplicate the length of the rope (R'=2R) to get

Step-by-step explanation:
The equation of the centripetal force is given by:


Where:
R is the length of the rope
m is the mass of the object
v is the speed of the object
If we want to reduce the centripetal force in half, we can duplicate the length of the rope (R'=2R), which means:



I hope it helps you!