Blocks being pulled by a string

[alexialight]

I'm just starting to get my head around the concepts of Tension and Force but I'm stuck on this question, I was wondering if anyone could help me out?

Q: 3 identical blocks connected by ideal strings are being pulled along a horizontal frictionless surface by a horizontal force F. The magnitude of the tension in the string between blocks B and C is T. Assume that each block has mass m.

i> What is the magnitude of the force? (Expressed in terms of T)
ii> What is the magnitude of the acceleration of the three blocks (in terms of m and F)?

I worked out the acceleration on block B (T/(2*m)) but don't know what to do next. I'd really appreciate any help with this.

 

[IntuitioN]

The acceleration is the same for the entire system. So the force must be (m1 + m2 + m3)*a

hope that helps

 

[alexialight]

I think it does... that would make the Force 3/2*T right?
So in terms of m and F, the acceleration would be F/3m ?

 

[ramollari]

Yes, you are right.

$$F - T = m_ca$$,

or

$$F = T + m_ca = T + m(\frac{T}{2m}) = \frac{3}{2}T$$

 

[alexialight]

Awesome - Thanks a lot