Particle Dynamics and Time Problem

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Discussion Overview

The discussion revolves around the dynamics of a falling particle, specifically focusing on the relationship between acceleration, velocity, and time as the particle approaches terminal velocity. Participants explore how to express the variation of acceleration and determine the time required for the velocity to be less than terminal velocity.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant states that the initial acceleration of a falling particle is equal to g and diminishes to zero, leading to a constant terminal velocity vf.
  • Another participant seeks clarification on whether the goal is to find the time when the velocity equals vf or when it is less than vf.
  • A participant specifies the objective as finding the time for the velocity to become less than vf.
  • There is a request for guidance on how to start solving the problem, indicating a need for foundational steps.
  • One participant suggests equating forces and gravitational effects as a starting point for the solution.
  • Another participant proposes setting up the ordinary differential equation for the velocity over time.
  • A participant questions the formulation of the differential equation and asks for clarification on how to express it correctly.
  • There is a follow-up inquiry about determining when the velocity will be less than the terminal velocity.

Areas of Agreement / Disagreement

Participants express uncertainty about the formulation of the problem and the correct approach to finding the time for the velocity to be less than terminal velocity. There is no consensus on the method to solve the problem or the specific conditions to be met.

Contextual Notes

Participants have not fully resolved the mathematical steps needed to express the relationship between acceleration, velocity, and time, and there are dependencies on definitions of terms like terminal velocity.

s4orce
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When a particle fall through the air, its initial acceleration a=g diminishes until it is zero, and thereafter it falls at a constant or terminal velocity vf. If this variation of the acceleration can be expressed as a=(g/v^2f)(v^2f-v^2), determine the time needed for the velocity v<vf. Initially the particle falls from rest.
 
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did you mean find the time when v=vf or terminal velocity?
 
find the time for the velocity to become v<vf. (V less than Vf)
 
So, how are you going to start the problem?
 
make the forces and gravitation = to each other? can you help me please?
 
s4orce said:
make the forces and gravitation = to each other? can you help me please?

Start up by setting the ordinary differential equation, dv/dt.
 
dv/dt = (g/v^2f)(v^2f-v^2)? like that? how? can you please show me
 
Ok now, when will v be less than the terminal velocity?
 

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