# Two blocks attached by a string(dynamic)

1. Homework Statement
Two blocks (m1=4.0kg, m2=7.5kg) are attached by a light cord pulled along a horizontal surface by a force of 53N as shown in the diagram. If the coefficient of friction between the blocks and the surface is 0.30, what is the tension in the rope between the two blocks.

M2 -------- M1 ------->Force applied

2. Homework Equations
Fnet= Ma

3. The Attempt at a Solution

I used the Fnet=ma, on m1 i got Fapplied - T - Ff = ma
But i dont know how to find the acceleration. And i know theres two different frictions because of two different mass. So i dont know how to join them together and find Tension.

ps: I just joined this forum, What should i do if i have a a lot of questions or simply want someone to check over my assignment for me before I hand them in? (got like 20-30questions). I dont want to violate the rule so im just wondering if theres a specific section to post or something.

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Apply Newton2 to M2 and then you'll have 2 equations to work with.

If you have other questions you want to post, then create a new thread for each one.

Hmm, ok so now i got this.

m1:
Fnet=m1a
Fapplied-T-Ff=m1a

m2:
Fnet=m2a
T-Ff=m2a
a=T-Ff/m2

plug a into m1's equation

Fapplied-T-Ff=m1(T0Ff/m2)
53-T-(0.30x4.0x9.8)=4.0(T-0.30x7.5x9.8/7.5)
53=1.53T
T=34.565N = 35N

If someone can check if i did the calculation right, it would be greatly appreciated.

Thank you.

Yes, this is correct :)