three blocks with masses m, 2m, and 3m

Hello there!

Greetings!

I am extremely sorry to tell you dear but you haven't completed your question, please do let me know the complete question so that I can help you with its solution. But if in your question , if the the system is moving with constant velocity and you have been asked to find the force then it will be 0 as acceleration will be zero as velocity is constant. And we know that force is equal to mass multiplied with net acceleration so F=ma=0 (a=0). Thus force is 0.

Thankyou