Three blocks with masses m, 2m and 3m are connected by strings, as shown in the figure. After an upward force F is applied on block m, the masses move upward at constant speed v. What is the net force on the block of mass 2m? (g is the acceleration due to gravity)

6 mg zero 2 mg 3 mg

zero

F=mass × acceleration the blocks are moving with constant velocity hence there will be no acceleration F = 0