Will Block M2 Move Left? Understanding Forces in a Connected Spring System"

In summary: If the mass of the object being compressed is greater than the mass of the object providing the compression force, then the object will be pushed. If the mass of the object being compressed is less than the mass of the object providing the compression force, then the object will be pulled.
  • #1
navneet9431
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Suppose two blocks m1 and m2,connected by a spring are kept on a frictionless surface and the block m1 is applied an external force F.
My teacher taught me that in a spring the force is generated in the direction opposite to the displacement of the spring.
So the spring would generate a force in the left direction as it's displacement would be right.
So my question is that will the block m2 move in the *left* direction or not as a force is getting applied on it in the left direction?
I will be thankful for help!
 

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  • #2
What would happen, if the mass of block ##m_2## would be zero? What would be the force on ##m_1##? Try to apply Newton's 3rd law.
 
  • #3
If mass of m2 is zero then block m1 would just move with acceleration F/m1.
What are you trying to explain?
stockzahn said:
What would happen, if the mass of block ##m_2## would be zero? What would be the force on ##m_1##? Try to apply Newton's 3rd law.
 
  • #4
navneet9431 said:
If mass of m2 is zero then block m1 would just move with acceleration F/m1.
What are you trying to explain?

There only would be a force to the left acting on ##m_1## if there is a "counterforce" acting to the right on ##m_2##. From the perspective of ##m_2## the displacement of the spring would be to the left.
 
  • #5
navneet9431 said:
My teacher taught me that in a spring the force is generated in the direction opposite to the displacement of the spring.
Have you never compressed/stretched a spring with your hands? It should be obvious that it applies two opposite forces at both ends.
 
  • #6
The teacher's question is not tightly enough specified for a rigorous answer. This is not as harmless a fault as you might think because two different people could interpret it in two different ways.
If we assume that the spring is at its equilibrium length then what would cause any movement to the left if the input force F is to the right?
What do we know about the forces at each end of a light spring or a light string?
 
  • #7
navneet9431 said:
My teacher taught me that in a spring the force is generated in the direction opposite to the displacement of the spring.
The spring resists being compressed or being stretched. Here, the spring is compressed and it will exert an outward force at each end.
 
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