What is the solution to the Kinematics of Particles Homework?

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Homework Help Overview

The discussion revolves around a kinematics problem involving forces acting on a particle before and after a string is cut. Participants are analyzing the forces in the vertical direction and the implications of their calculations on tension and gravitational forces.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss summing forces in the y direction, questioning the use of trigonometric functions in their calculations. There are attempts to clarify the setup of diagrams and the direction of axes, as well as the implications of these choices on the analysis.

Discussion Status

Some participants have provided feedback on the original poster's approach, suggesting a review of the calculations and the assumptions made regarding the angles and forces involved. There is an ongoing exploration of the correct interpretation of the forces acting on the particle.

Contextual Notes

Participants note the importance of clearly defining the axes in their diagrams and the role of gravitational force in their calculations. There is mention of a specific angle (40 degrees) that influences the components of the forces being analyzed.

Auburn2017
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Homework Statement


Refer to figure please.

Homework Equations


∑Fy=0 before string is cut

The Attempt at a Solution


I tried summing the two forces in the y direction before the strings were cut which would be the two tensions at a sin40° and minus the weight of the ball(mg). That gave me T in terms of mg. Then I summed the forces when the string was cut and got T minus mgcos40. Then I thought that would be my ratio but my answer didnt match that of the solution. Help Please!
 

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Your approach seems good. Are you sure that you should be using cos40o in the calculation after the string is cut? You left out the details of your calculations and you did not state what you actually got for the tension before and after one of the strings is cut.
 
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TSny said:
Your approach seems good. Are you sure that you should be using cos40o in the calculation after the string is cut? You left out the details of your calculations and you did not state what you actually got for the tension before and after one of the strings is cut.
This is what I ended up doing. Does my work look right or did I just happen to get it right? Oh and there should be a mg on the end of my T=0.643 equation. I don't really know why I used mgsinΘ, I just know it gets you the right answer. An explanation on that would be greatly appreciated.
 

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In your first diagram your analysis looks good. Here you are taking the y-axis to be vertically upward.

In your second diagram (one string), what direction are you taking for the y-axis? Also, you should show the gravitational force in this diagram.
 
TSny said:
In your first diagram your analysis looks good. Here you are taking the y-axis to be vertically upward.

In your second diagram (one string), what direction are you taking for the y-axis? Also, you should show the gravitational force in this diagram.
Oh that is what it is. If you take the y-axis to be at an angle of 40 degrees then the y component of the weight becomes mg sin40. Makes sense now.
 
OK. Good work.
 
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