How Do You Calculate the Velocity of a Counterweight Relative to an Elevator?

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Homework Help Overview

The problem involves calculating the velocity of a counterweight relative to an elevator, given that a winch draws a cable at a constant rate. The context is rooted in mechanics, specifically dealing with motion and relationships between different components in a pulley system.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the equations used to relate the velocities of the winch, elevator, and counterweight. There are attempts to derive relationships based on the movement of the winch and the implications for the elevator's motion. Questions arise regarding the correctness of the equations and the assumptions made about the system.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some have suggested reconsidering the relationship between the winch's speed and the elevator's speed, while others have expressed uncertainty about their calculations and the equations being applied.

Contextual Notes

There is a noted lack of clarity regarding the speed of the elevator and how it relates to the counterweight's motion. Participants have pointed out that specific working details are missing, which may hinder the ability to assess the equations being used.

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Homework Statement



In the sketch at right, the winch W draws the cable at a constant rate of 2 m/s.
Calculate the velocity of the counterweight C relative to the elevator E.

Homework Equations



(Sa-Sc)+(Sb-Sc)+Sb=I2

The Attempt at a Solution



I must be using the wrong equation because I am getting really strange answers.
 

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deveny7 said:
I must be using the wrong equation because I am getting really strange answers.
Perhaps, perhaps not, we're unable to say either way since you haven't included your working for us to see what equation/s you are using.

Q: How fast is the elevator rising?
 
I used 4Vw +Vc = 0. Which means the elevator would rise at 8m/s but that can't be right.
 
Think about it in terms of the amount of rope wound in. If the winch winds in 2m the elevator goes up 1m. So the elevator moves up at half the speed of the winch eg 1m/s

Then look at the elevator and counter weight. If the elevator were raised say 1 meter how far does the counterweight move relative to the platform? How far does it move relative to the elevator?
 

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