Two pendulums banging into each other problem.

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Homework Help Overview

The problem involves two pendulums, A and B, with given masses and conditions of motion, specifically focusing on their collision dynamics and the application of conservation of momentum. The context is rooted in mechanics, particularly the behavior of pendulums and momentum transfer during collisions.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the conservation of momentum as a potential approach, with one participant attempting to equate the velocities of the pendulums at the moment of collision. There is also a consideration of the implications of the collision direction on momentum calculations.

Discussion Status

The discussion is ongoing, with participants providing hints and questioning the assumptions made about the velocities of the pendulums. There is recognition that the original height of the pendulums is necessary for determining their velocities, and some guidance has been offered regarding the use of the period of a pendulum to find relevant values.

Contextual Notes

Participants note that the time taken for the pendulums to swing is not sufficient to deduce their velocities without additional information about the height from which they were released. The problem setup includes variables that are not fully defined, leading to challenges in solving for the mass of pendulum B.

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Homework Statement



A system contains two metal balls hanging from strings of length !.0 m. Pendulum A has a mass of 2.0 kg and B has a period of 2.0s. They are released from the same height at the same time and collide right in the middle of their arcs. If pendulum A comes to a complete stop while B moves backwords with half of its original speed, what is the mass of pendulum B?

Homework Equations



Conservation of momentum.


The Attempt at a Solution



My first thought was the conservation of momentum. 2Va+MbVb=-(1/2)MbVb. Of course there's 3 variables so i couldn't solve it but then i thought that since the balls were colliding in the middle of their arcs that maybe they're velocities were the same. So Va=Vb. From that logic I get that the mass of B is -4/3 which obviously makes no sense... I am not sure what I am doing wrong. I am gratful for any help. Thanks in advance
 
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tjhero123 said:

Homework Statement



A system contains two metal balls hanging from strings of length !.0 m. Pendulum A has a mass of 2.0 kg and B has a period of 2.0s. They are released from the same height at the same time and collide right in the middle of their arcs. If pendulum A comes to a complete stop while B moves backwords with half of its original speed, what is the mass of pendulum B?

Homework Equations



Conservation of momentum.


The Attempt at a Solution



My first thought was the conservation of momentum. 2Va+MbVb=-(1/2)MbVb. Of course there's 3 variables so i couldn't solve it but then i thought that since the balls were colliding in the middle of their arcs that maybe they're velocities were the same. So Va=Vb. From that logic I get that the mass of B is -4/3 which obviously makes no sense... I am not sure what I am doing wrong. I am gratful for any help. Thanks in advance


The momentum is a vector. The balls move in opposite directions just before they collide. Va is not equal to Vb.


ehild
 
Use the equation for the period of a pendulum to help you find Vb.
 
tannerbk said:
Use the equation for the period of a pendulum to help you find Vb.
The time taken is irrelevant. You cannot deduce any actual velocity since you do not know the original height. ehild's hint is the way forward.
 

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