Q in dynamics, kinetics, Energy

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Discussion Overview

The discussion revolves around a physics homework problem involving a 1 kg block sliding on a circular rod under the influence of a force. Participants explore the concepts of work, energy, and the calculations necessary to determine the speed of the block at a specific point.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • The initial energy at point A is stated to be zero, while the energy at point B is expressed as mgh + 0.5mv².
  • One participant suggests using the work done formula, which involves the force and displacement, and recommends integrating over the path of motion.
  • Another participant describes their attempt to calculate the displacements in both the X and Y directions and expresses confusion over the integration process from 0 to π/2.
  • A later reply requests to see the participant's work to better understand the issue they are facing.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correct approach to calculating the work done by the force, as one participant expresses confusion about their integration results.

Contextual Notes

There are unresolved aspects regarding the integration process and the assumptions made about the displacements in the context of the circular motion.

vemplord
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Homework Statement



1 Kg block slides on a circular rod (no friction) from rest in A position by a force of 40N. What is the speed when it reached point B. (see attached pic)


Homework Equations



W(f)=E(B)-E(A)

The Attempt at a Solution


The energy in A is 0, the energy in B is mgh+0.5mv^2
My problem is how to find the work of the force.

Thx.
 

Attachments

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Welcome to PF!

Hi vemplord! Welcome to PF! :smile:

(try using the X2 tag just above the Reply box :wink:)
vemplord said:
My problem is how to find the work of the force.

Work done = force "dot" displacement …

so for a small angle dθ, find the displacement, "dot" it with the force, and then integrate. :smile:
 
Thanks,

I tried that:
The Y displacement is rsinθ an X displacement is r-rcosθ, tried to integrate from "0" to "π/2" but it doesn't come out right.

What am i doing wrong?
 
vemplord said:
Thanks,

I tried that:
The Y displacement is rsinθ an X displacement is r-rcosθ, tried to integrate from "0" to "π/2" but it doesn't come out right.

What am i doing wrong?

dunno :redface:show us! :smile:
 

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