Non-Uniform Circular Motion problem

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Homework Help Overview

The problem involves a ball swinging in a vertical circle, with specific details about its acceleration at a given angle. The context is centered around non-uniform circular motion and the components of acceleration.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss how to approach the vector diagram and the implications of the angle given in the problem. There are questions about the direction of the angle and its relevance to the solution.

Discussion Status

Some participants have provided insights into the vertical nature of the circle and the forces acting on the ball, while others are still seeking clarity on the angle's direction and its impact on the problem. There is an ongoing exploration of how to represent the situation graphically.

Contextual Notes

Participants note the lack of explicit direction for the angle and how this might affect the interpretation of the acceleration components. There is also mention of the need for a clear diagram to aid understanding.

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"Non-Uniform Circular Motion" problem

Homework Statement


A ball swings in a vertical circle at the end of a rope 1.50 m
long. When the ball is 36.9° past the lowest point on its
way up, its total acceleration is (-22.5 i + 20.2j) m/s^2. At
that instant, (a) sketch a vector diagram showing the components
of its acceleration, (b) determine the magnitude
of its radial acceleration, and (c) determine the speed and
velocity of the ball.



Homework Equations


a = v^2 / r
a(total) = a(tangent) + a(radial)


The Attempt at a Solution


For starters, I don't even know how to approach a), in all honesty. Since the problem doesn't tell me in which direction the rope is spinning, I don't know where to start. However, I have a feeling that the problem doesn't need to tell me this based on the information regarding total acceleration.
Also, even though the total acceleration is expressed in that format, I seriously doubt that the unit vectors are ar and at. If I knew how to draw this, I'll probably be able to figure out the rest of the problem...
 
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It's a vertical circle.There is the weight of the ball downwards and tension of string at an angle.
And yes the unit vectors i and j are not along the radial and transverse directions. If you would draw the problem keeping in mind that the plane of the circle is vertical it would be easier.
 


All right, I get that much. However, I'm still unable to determine if it's 36.9o to the left, or to the right...
 


How does it matter?
 


[PLAIN]http://photos-a.ak.fbcdn.net/hphotos-ak-snc1/hs030.snc1/3190_91017112564_509877564_2512520_5779508_n.jpg

According to this solution, it does...
 
Last edited by a moderator:


Bump.

I don't mean to offend anybody, but can anyone explain why the solution goes 36.9 degrees to the right, and no to the left?
 


If you were to look at the setup from the other side the rope would go left. If the diagram is already sketched there is no harm in referring the directions as left or right for convenience.
 


So you're saying that I could draw it in either direction, and I could still get the diagram, along with b) and c) correct. Am I following you correctly?
 


Bump...
 
  • #10


yes.
 

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