Answer:
F' = 9 F
Step-by-step explanation:
The question says that, "If the linear speed of a mobile moving with MCU is tripled and the radius remains constant, then the centripetal force:"
The formula for the centripetal force is given by :

Where
m is the mass of the object
v is the velocity
r is the radius of path
If the linear speed us tripled, v' = 2v, r = constant, then the new centripetal force is given by :

So, the new force becomes 9 times of the initial force.