Blocks being pulled by a string

In summary, the conversation discusses the concepts of Tension and Force in relation to three identical blocks connected by strings on a frictionless surface. The question at hand is determining the magnitude of the force and acceleration in terms of T and m. The group works through the solution, with the final conclusion being that F is equal to 3/2*T and the acceleration is F/3m. The conversation ends with gratitude for the help and confirmation that the solution is correct.
  • #1
alexialight
7
0
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 accleration 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.
 

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  • #2
The acceleration is the same for the entire system. So the force must be (m1 + m2 + m3)*a

hope that helps
 
  • #3
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 ?
 
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  • #4
Yes, you are right.

[tex]F - T = m_ca[/tex],

or

[tex]F = T + m_ca = T + m(\frac{T}{2m}) = \frac{3}{2}T[/tex]
 
  • #5
Awesome - Thanks a lot
 

1. How does pulling a string affect a block?

When a string is pulled, it exerts a force on the block that causes it to move in the direction of the string's pull. This is because the string is attached to the block and acts as a link between the force exerted by the person pulling the string and the block itself.

2. What factors affect the movement of a block being pulled by a string?

The movement of a block being pulled by a string is affected by several factors, including the tension in the string, the weight of the block, the angle at which the string is pulled, and any friction between the block and the surface it is resting on.

3. Can the direction of the string's pull change the movement of the block?

Yes, the direction of the string's pull can greatly affect the movement of the block. For example, if the string is pulled at an angle, the block will move in a diagonal direction rather than straight ahead. Additionally, changing the direction of the pull can also change the speed and acceleration of the block.

4. What is the difference between a fixed and free end of a string?

A fixed end of a string is securely attached to a surface, while a free end is not attached to anything. When pulling a block with a string, the fixed end will generally remain in place while the free end moves with the block. However, if the string is not taut or the force pulling the string is strong enough, both ends may move.

5. How does the weight of the block affect the tension in the string?

The weight of the block is directly related to the tension in the string. As the weight of the block increases, the tension in the string also increases. This is because the string must support the weight of the block and the force of the person pulling the string, resulting in a greater tension force.

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