Conical pendulum: what are the tension and the angle?

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SUMMARY

The discussion centers on a physics problem involving a conical pendulum, where a 1.5 kg rock is whirled in a horizontal circle with a string length of 0.8 m and a constant speed of 5 m/s. Participants debate the sufficiency of the provided information to solve for the tension in the string and the angle of the pendulum. Key equations referenced include Fc = mv²/r and W = mg, indicating that the problem can be approached algebraically without numerical substitution until the final steps.

PREREQUISITES
  • Understanding of circular motion dynamics
  • Familiarity with trigonometric relationships, specifically sin(θ) and cos(θ)
  • Knowledge of Newton's laws of motion
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Study the derivation of tension in conical pendulum systems
  • Learn how to apply the equation Fc = mv²/r in various contexts
  • Explore the relationship between sine and cosine functions in trigonometry
  • Review examples of similar physics problems in high school textbooks
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and circular motion, as well as educators looking for examples of conical pendulum problems.

pkc111
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Homework Statement
A rock with a mass 1.5 kg is being whirled in a horizontal circle on a string 0.8 m long. The speed of the rock is a constant 5 m/s. Find the magnitude and direction of the tension in the string.
COMMENT: There seems to be too many unknowns here.
Relevant Equations
Fc = mv2/r
W = mg
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1585533348673.png
 
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pkc111 said:
Homework Statement:: A rock with a mass 1.5 kg is being whirled in a horizontal circle on a string 0.8 m long. The speed of the rock is a constant 5 m/s. Find the magnitude and direction of the tension in the string.
COMMENT: There seems to be too many unknowns here.
Relevant Equations:: Fc = mv2/r
W = mg

View attachment 259616View attachment 259617
So what is cos2(θ) in terms of sin(θ)?

By the way, it is far better style to keep everything algebraic. Don't plug in numbers until the end. For one thing, more people will take the trouble to check your work.
 
Thank you for your reply.
Are you saying that this question is solvable with the information provided in the question?
 
Cos my gut feeling is the question is wrongly written ..as every other question in this high school physics textbook chapter needs only very straightforward maths...Is someone able to say whether the information is enough to define a specific conic pendulum case which is solvable?
 
pkc111 said:
Thank you for your reply.
Are you saying that this question is solvable with the information provided in the question?
In your last equation in post #1 there is only one unknown, so it should be solvable.
I repeat, what equation relates sin to cos (and involves no other trig function)?
 

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