What is the solution to the Kinematics of Particles Homework?

In summary, the conversation discusses the calculation of tension before and after a string is cut in a physics problem, using the equation ∑Fy=0 before the string is cut. The approach is to sum the two forces in the y direction before the string is cut, which gives T in terms of mg, and then to sum the forces after the string is cut, which gives T minus mgcos40. There is some confusion over the use of cos40 in the calculation and the direction of the y-axis in the second diagram. The final conclusion is that taking the y-axis to be at an angle of 40 degrees results in the correct answer.
  • #1
Auburn2017
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1

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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  • #2
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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  • #3
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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  • #4
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.
 
  • #5
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.
 
  • #6
OK. Good work.
 
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Related to What is the solution to the Kinematics of Particles Homework?

1. What is Kinematics of Particles?

The Kinematics of Particles is a branch of physics that studies the motion of particles without considering the forces that cause the motion. It involves analyzing the position, velocity, and acceleration of a particle as it moves through space and time.

2. What is the difference between displacement and distance in Kinematics of Particles?

Displacement refers to the change in position of a particle in a specific direction, while distance is the total length of the path traveled by the particle. Displacement is a vector quantity, while distance is a scalar quantity.

3. How is velocity calculated in Kinematics of Particles?

Velocity is calculated by dividing the change in position (displacement) by the change in time. It is a vector quantity and includes both magnitude (speed) and direction.

4. What is the difference between speed and acceleration in Kinematics of Particles?

Speed refers to the rate at which an object is moving, while acceleration is the rate at which the speed is changing. Acceleration can also be described as the change in velocity over time.

5. How is Kinematics of Particles used in real-life applications?

Kinematics of Particles has many real-life applications, including in the design and analysis of vehicles and machines, sports, and other forms of motion. It is also used in navigation and GPS systems, as well as in understanding the motion of celestial bodies in space.

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