Relative velocity and force relationship

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Discussion Overview

The discussion revolves around determining the force exerted during a collision between two components traveling in the same direction at different velocities. Participants explore the relationship between relative velocity, mass properties, and the time factor involved in the collision, with a focus on practical applications and experimental approaches.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks to find the force during a collision given the relative velocity and mass properties of the components, expressing uncertainty about the time to consider in the calculation.
  • Another participant suggests that knowing the time of contact would allow for calculating impulse from momentum change to derive force.
  • A different participant points out that the duration of contact varies significantly between different materials, such as water balloons versus steel blocks, complicating the force calculation.
  • One suggestion involves using accelerometers on the components to gather data during the collision.
  • Another participant notes that the problem is often encountered in contexts like car crashes, emphasizing the need for detailed structural information about the components due to deformation during collisions.
  • A later reply proposes experimenting to find the 'spring constant' of the components, treating them as colliding springs to estimate forces based on potential energy during contact.
  • One participant mentions that certain objects have limits on compression to avoid damage, which could help establish a lower bound on the forces involved.

Areas of Agreement / Disagreement

Participants express varying opinions on how to approach the problem, with no consensus on a definitive method for calculating the force during the collision. Multiple competing views and uncertainties remain regarding the necessary information and assumptions.

Contextual Notes

Participants highlight limitations such as the dependence on the specifics of the collision (e.g., material properties, deformation) and the need for additional information about the time of contact to accurately calculate force.

k.udhay
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This is something related to my job.

There are two components A & B both traveling the same direction but at a different velocity. I can find out the exact velocity of both the components when they just hit each other, thus relative velocity is known.

Is there a way I find out the force exerted during this collision? I know the mass properties (mass & inertia) of A & B.

Pl. help

P.s. - I am aware that force is a function of acceleration (and hence time). However, I am clueless here as what time to be considered.
 
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k.udhay said:
This is something related to my job.

There are two components A & B both traveling the same direction but at a different velocity. I can find out the exact velocity of both the components when they just hit each other, thus relative velocity is known.

Is there a way I find out the force exerted during this collision? I know the mass properties (mass & inertia) of A & B.

Pl. help

P.s. - I am aware that force is a function of acceleration (and hence time). However, I am clueless here as what time to be considered.

If you knew something about the time, you could work out the impulse from the change in momentum and then work out the force from the time over which the collision took place.
 
You can't solve it without more information. Clearly two water balloons would be in contact with each other for longer than two blocks of steel during similar velocity collisions.
 
Can you put accelerometers on your components?
 
This is the sort of question that's often asked in the context of car crashes and personal injuries (punches etc.) and the 'force' of the collision is what people want to know. And it's really hard! To find it, you need to know the details of the structure of the two components because they will deform whilst the momentum is re-arranged between them. It may be that you don't actually need to know those details - unless you are worried about damage - and you can assume a perfectly elastic or totally inelastic collision and that can give you some bounds for the resulting motion.
 
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@k.udhay If you are able to do some experimenting, you could find the 'spring constant' of the components and treat them as colliding springs. With a bit of ingenuity, you could work out the Potential Energy in the springs during contact and that could tell you the sort of forces acting. Whether it would be worth going into all that would depend on your facilities and technical know how.
 
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Some objects clearly cannot be compressed more than a certain amount during a collision or damage will occur. You can probably use that to set a lower bound on the forces involved.
 

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