Quick Pendulum and Trig Question

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SUMMARY

The height a pendulum swings is calculated using the formula h = r(1 - cos(θ)), where r represents the length of the pendulum string and θ is the angle of swing. This relationship is derived from the geometry of a right triangle formed by the pendulum's position. The hypotenuse of this triangle is the length of the string, r, and the adjacent side can be determined using the cosine function. Understanding this concept is essential for solving related physics problems involving pendulum motion.

PREREQUISITES
  • Basic understanding of trigonometric functions, particularly cosine.
  • Familiarity with right triangle properties and definitions.
  • Knowledge of pendulum mechanics and motion.
  • Ability to manipulate and solve algebraic equations.
NEXT STEPS
  • Study the derivation of the pendulum height formula h = r(1 - cos(θ)).
  • Explore the applications of trigonometry in physics, specifically in oscillatory motion.
  • Learn about the relationship between angular displacement and linear displacement in pendulums.
  • Investigate the effects of varying string length and angle on pendulum dynamics.
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Students studying physics, particularly those focusing on mechanics and oscillatory motion, as well as educators looking for clear explanations of pendulum behavior.

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Homework Statement


This is taken from a much larger problem, but I only need the answer to one particular question. Please help me understand why the height that a pendulum swings is r(1-cos\theta) where r is the length of the string and theta is the angle it swings through.

Homework Equations



h = r(1-cos\theta)

The Attempt at a Solution



I'm afraid trigonometry's one of my weakness. I can't begin to understand why this is the case. I'm sure it involves a crazy mess of right triangles.
 
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If you draw a vertical line to represent the pendulum at initial position and then draw it at a general angle, if you draw a horizontal line from the bob to meet the vertical line, you will get a right angled triangle.

In the right angled triangle, the hypotenuse is 'r'.

So what is the adjacent side of this triangle in terms of 'r' and the angle? (Hint: use cosine)
 
Ah, okay. I see now. Thank you!
 

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