Centripetal Force and Tension in Rotating System

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SUMMARY

The discussion centers on calculating the tension in the lower string of a rotating system involving a 1.0 kg ball attached to a rigid vertical rod by two massless strings, each 1.0 m long. The system forms an equilateral triangle configuration as it rotates. The relevant equation for this scenario is F = mv² / r, where F represents centripetal force, m is mass, r is the radius, and v is velocity. Participants emphasize the importance of a free-body diagram to identify all forces acting on the ball, including gravity and the tensions in the strings.

PREREQUISITES
  • Understanding of centripetal force and its calculation using F = mv² / r
  • Knowledge of free-body diagrams and how to analyze forces acting on objects
  • Familiarity with the concepts of tension in strings and their role in rotational dynamics
  • Basic principles of rotational motion and equilibrium in physics
NEXT STEPS
  • Study the derivation and application of centripetal force equations in rotating systems
  • Learn how to construct and analyze free-body diagrams for complex systems
  • Explore the effects of varying rotational speeds on tension in strings
  • Investigate the conditions under which strings break in a rotating system
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, rotational dynamics, and tension in strings. This discussion is beneficial for anyone tackling problems related to centripetal force and free-body diagrams.

Kaos_Griever
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Homework Statement
A 1.0kg ball is attached to a rigid vertical rod by the means of two massless strongs each 1.0m long. The strings are attached to the rod at points 1.0m apart. The system is rotating about the axis of the rod, both strings being taut and forming an equilateral triangle with the rod. The tension in the supper string is What is the tension in the lower string? What is the net force on the ball? What is the speed of the ball?

Relevant equations
The only equation I can think of is F = mv^2 / r
where m = mass, r = radius, v = velocity, F = Centripetal Force


The attempt at a solution
I'm not sure how to do the entire question... does finding the tension need an angle? Because the string is not at the horizontal...
 
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At first glance, (and maybe I'm missing something) but it seems that something is missing. If you spin the rod faster and faster (once you've reached the point at which both strings are taut), the tension in the strings will increase until they finally break, and will continue to form an equilateral triangle.

Is it implied in the problem that the system is rotating "just fast enough" for the lower string to be taut?

However, on problems where forces are important, it's a good idea to draw a free-body diagram. What forces are acting on the ball? (You're missing one; usually one which is obvious)
 
No other forces have been given to me in the question. I am also not sure of the forces that will be acting on the free body diagram of the ball? Would it only be the force of gravity, the normal force, and the forces of the strings...?
 
Yes, the force of gravity = you just had a mass there; I was making sure you were including that force.
 
Kaos_Griever said:
No other forces have been given to me in the question. I am also not sure of the forces that will be acting on the free body diagram of the ball? Would it only be the force of gravity, the normal force, and the forces of the strings...?
I believe you left out a given..the tension in the upper string is ?
 

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