Homework Help Forum: Help Physics 1 question

Posted by Ellie on Thursday, November 5, 2009 at 1:06am.

Period=1.4 seconds gravitational acceleration=9.8 m/s^2 length of string=.4865m angle is 3 degrees acceleration from that angle is=.5129 m/s^2 change in bobs height from release to bottom of arc=.000667m bobs speed at bottom of arc=.1143 m/s so i done all the questions and calculations for one above but i not sure how to do this one. Any help is appreciated. Describing a pendulum as a harmonic oscillator requires the use of the small angle approximation. What is the magnitude of the difference between the actual acceleration (without using the small angle approximation) and the approximate acceleration (using the small angle approximation)? The answer is a very small number. As for all other numerical answers, provide your answer with 4 significant digits.

• Help Physics 1 question - drwls, Thursday, November 5, 2009 at 1:20am

  Assume that the angle is 3 degrees = 0.05235988 radians. The actual acceleration of the pendulum in the direction of motion, when A = 3 degrres, is g sin A = 9.81 * 0.05233596 = 0.51341573 m/s^2 The small angle approximation says that the acceleration is g * A(in radians) = 0.51376504 m/s^2 Take the difference and keep 4 siginificant figures. It would also be useful to express it as a percentage.

  
  

• Help Physics 1 question - Ellie, Thursday, November 5, 2009 at 1:31am

  i tried .0003493 and -.0003493 but both are wrong where am i messing up exactly?

  
  

• Help Physics 1 question - MathMate, Thursday, November 5, 2009 at 5:20pm

  Ellie, If you had redone the calculations, you would have found that the value for the small approximation is 0.51365039886193 instead of 0.51376504 which makes the difference 0.0002347, and after rounding to 4 significant figures as required by the question, will become 0.0002 m/s². See also my previous responses, corrected for parts d and e at: http://www.jiskha.com/display.cgi?id=1257393909

  
  

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