Force applied to 2 connected mass.

[negation]

A force is applied to m₁ connected to m₂ by a "massless" cord. where m2>m1.

the acceleration, a, is a = F/m₁+m₂

By decomposing the system into A and B where A refers to the tension on m₁ upon having the force applied onto m₂, the tension T_A is to the positive x-direction.

However, in the case of the system B, the tension T_B is to the negative x-direction as the force F is applied directly to m₂.

Why does T_B arises in the block m₂ but yet not in m₁?

 

[Doc Al]

Why does T_B arises in the block m₂ but yet not in m₁?

I'm not sure I understand this statement. The cord connecting the two masses exerts a tension force on both m₁ and m₂. The cord exerts the same force on both blocks (different directions, of course).

 

[negation]

I'm not sure I understand this statement. The cord connecting the two masses exerts a tension force on both m₁ and m₂. The cord exerts the same force on both blocks (different directions, of course).

I shall rephrase. I was lacking clarity in the OP.

When force F is applied on m₂, m₁ experiences a tension T_A in the positive x-direction. (why shouldn't m₁ experience another tension in the negative x-direction. By my understanding, there should be an equal and opposite reaction.

In the case of m₂, upon the appliance of the force F, the m₂ experience not only the force F in the positive x-direction but also a tension T_B in the negative x-direction.

 

[Doc Al]

When force F is applied on m₂, m₁ experiences a tension T_A in the positive x-direction.

Right. Tension is created in the cord, which acts on both masses.

(why shouldn't m₁ experience another tension in the negative x-direction.

What would create that tension?

By my understanding, there should be an equal and opposite reaction.

A reaction from what?

In the case of m₂, upon the appliance of the force F, the m₂ experience not only the force F in the positive x-direction but also a tension T_B in the negative x-direction.

And if the mass m₁ were connected to a third mass, then it too would experience a tension force acting to the left. But there is no third mass.

(Note that the force F and the tension in the cord are not equal.)

 

[negation]

Right. Tension is created in the cord, which acts on both masses.


What would create that tension?


A reaction from what?


And if the mass m₁ were connected to a third mass, then it too would experience a tension force acting to the left. But there is no third mass.

(Note that the force F and the tension in the cord are not equal.)

A reaction from m₁ having experience a force F applied to m₂?

Suppose, as you've suggested that a third mass m₃ was attached to m₁ to the left. If the same force F were applied, then aside from m₂ having experienced the tension T_B, m₁ would now experience a tension in the negative x-direction, am I right?

 

[Doc Al]

A reaction from m₁ having experience a force F applied to m₂?

I'm not sure what you mean by a 'reaction'. m₂ pulls on m₁ (via the massless cord) and m₁ pulls back on m₂.

Suppose, as you've suggested that a third mass m₃ was attached to m₁ to the left. If the same force F were applied, then aside from m₂ having experienced the tension T_B, m₁ would now experience a tension in the negative x-direction, am I right?

Sure. The force F will end up creating various tensions in the cords connecting the masses.

 

[dauto]

I shall rephrase. I was lacking clarity in the OP.

When force F is applied on m₂, m₁ experiences a tension T_A in the positive x-direction. (why shouldn't m₁ experience another tension in the negative x-direction. By my understanding, there should be an equal and opposite reaction.

In the case of m₂, upon the appliance of the force F, the m₂ experience not only the force F in the positive x-direction but also a tension T_B in the negative x-direction.

Yes there is a reaction (Newton's 3rd law). What made you believe there isn't one?

 

[dauto]

I'm not sure what you mean by a 'reaction'. m₂ pulls on m₁ (via the massless cord) and m₁ pulls back on m₂.


Sure. The force F will end up creating various tensions in the cords connecting the masses.

Come on, Doc. he's talking about Newton's 3rd law. quoting from your post " m₂ pulls on m₁" - That's the action - "and m₁ pulls back on m₂" - That's the reaction.

 

[negation]

Yes there is a reaction (Newton's 3rd law). What made you believe there isn't one?

I understand there to be one but it isn't outlined by my lecturer.

 

[Doc Al]

Come on, Doc. he's talking about Newton's 3rd law. quoting from your post " m₂ pulls on m₁" - That's the action - "and m₁ pulls back on m₂" - That's the reaction.

That's why I used it as an example. But I don't think that's what was meant. (I think he was looking for a second force acting on the trailing block.)

 

[dauto]

I understand there to be one but it isn't outlined by my lecturer.

That doesn't mean it's not there.