inertia is the property of mass and it only depends on the mass of object
If speed of the cart is tripled and no change in the mass of object
then we can say that there is no change in the inertia of object
So here we can say that on increasing the speed the inertia will be same
as inertia depends on mass which is constant and it is equal to 12 kg
speed of the object is initially given as 0.25 m/s while if it is tripled then final speed will be 0.75 m/s