Calculating Contact Forces Between Three Blocks on a Frictionless Surface

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Homework Help Overview

The problem involves three blocks on a frictionless horizontal surface, where a force is applied to one block. Participants are tasked with determining the contact forces between the blocks given their equal masses and the applied force.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of Newton's second law and the calculation of acceleration. There are attempts to clarify the concept of contact forces between the blocks and the correct interpretation of forces acting on each block.

Discussion Status

Some participants express uncertainty about the terminology used regarding forces between the blocks and suggest focusing on the forces acting on individual bodies. There is a recognition of the correct calculation of forces, but also a questioning of the statements made about the relationships between the blocks.

Contextual Notes

Participants are navigating the nuances of force interactions and are considering the implications of Newton's third law in their discussions. The problem context emphasizes the importance of understanding forces in a system of connected bodies.

robvba
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Homework Statement


Three blocks on a frictionless horizontal surface are in contact with each other. A force F is applied to block A (mass mA ). If mA=mB=mC=10.0 kg and F = 96.0 N, determine the force of contact that each block exerts on its neighbor.


Homework Equations





The Attempt at a Solution



a=96/(10+10+10)=3.2N

contact force between mA and mB: 96-3.2*10=64
contact force between mB and mC: 3.2*10=32 or 64-3.2*10=32

did i solve this right?

thank you
 
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robvba said:
a=96/(10+10+10)=3.2N

contact force between mA and mB: 96-3.2*10=64
contact force between mB and mC: 3.2*10=32 or 64-3.2*10=32

Hi robvba! :smile:

Correct result … and it looks like you got it the right way, but I'm not sure.

This is a Newton's second law problem … you really shouldn't talk about the "force between" two bodies … each equation should only concern the forces on a particular body. :smile:
 
tiny-tim said:
Hi robvba! :smile:

Correct result … and it looks like you got it the right way, but I'm not sure.

This is a Newton's second law problem … you really shouldn't talk about the "force between" two bodies … each equation should only concern the forces on a particular body. :smile:

thank you. you're right. it's force of contact that each block exerts on it's neighbor. which would mean that block mA exerts a force of 64N on block mB while block mB exerts an equal and opposite force back; so mA = -mB. is that a fair statement?
 
robvba said:
thank you. you're right. it's force of contact that each block exerts on it's neighbor. which would mean that block mA exerts a force of 64N on block mB while block mB exerts an equal and opposite force back; so mA = -mB. is that a fair statement?

erm … I don't think you mean mA = -mB, do you?

I was thinking more of mass times acceleration = sum of forces …

you know the acceleration of block A, so the sum of forces on block A is … , and so the reaction force from block B on block A is … ? :wink:
 
tiny-tim said:
erm … I don't think you mean mA = -mB, do you?

I was thinking more of mass times acceleration = sum of forces …

you know the acceleration of block A, so the sum of forces on block A is … , and so the reaction force from block B on block A is … ? :wink:

right. i meant Fba = - Fab (Force of A on B = negative Force of B on A)...?
 

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