1. Need: Notebook CLASS Notes: Pendulum Lab with Clocks Handouts: Two reading (no notes) Two HW sheets Quiz Monday on pendulum problems Start Pendulum clock lab on Monday also Please Place Papers in the bin. If absent write dates on top Retake Dates See How They Run late -50% Barbie and Ken Lab late -20% Hooke’s Law QuizRedo by Friday Hooke’s Dry LabLate -50% ONLY Rewrite if NY Reaction time lab Late -50% All other tests and quizzes ONLY Retake if NY All other LabsLate -50% ONLY Rewrite if NY

2. Uses of a simple pendulum Simple pendulums are used to keep time in clocks in olden days. A simple pendulum is also used to calculate acceleration due to gravity g at various places on the earth and above the earth.

3. History of the pendulum The discovery of oscillatory motion of a pendulum and its properties are attributed to the famous astronomer Galileo.

4. Leaning Tower of Pisa, The story goes that as a small child he used to be taken to a cathedral in Pisa, Italy, by his parents.

5. The cathedral is next to the leaning tower of Pisa. History of the pendulum

6. Child Galileo was once bored listening to sermons in the cathedral. There were gas lamps hanging from the ceiling of the cathedral. History of the pendulum

7. Due to the breeze, the lamps were swinging from the ceiling. History of the pendulum

8. Galileo noticed that the swinging was periodic in nature by measuring time from the pulse or heart beats on his wrist.

9. He saw that the swinging lamp came to its one extreme position after a fixed number of beats on the heart beats on his wrist. History of the pendulum

10. Galileo later discovered the detailed the nature of simple pendulums and their properties.

11. Frequency: Pendulums Practice Problem on whiteboard Use your equation sheets Equation, substitute, solve with label. 1)A kid on a playground swing makes a complete to-and-fro swing each 2 seconds. The frequency of swing is _________. glenbrook.k12.il.us Do not leave answer as a fraction

12. Frequency: Pendulums Practice Problem on whiteboard Use your equation sheets Equation, substitute, solve with label. 2) A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ________. glenbrook.k12.il.us Do not leave answer as a fraction

13. PROBLEM: A man wants to know the height of a building which has a pendulum hanging from its ceiling. He notices that in one minute the pendulum oscillates 8 times. What is the frequency? f = 8/60 f=0.13 Hz or 0.13/sec or 0.13 sec -1 What is the Period, T? T=1/f T=1/.13 T=7.5 sec What is the total time, t? 60sec

14. PROBLEM: A man wants to know the height of a building which has a pendulum hanging from its ceiling. He notices that in one minute the pendulum oscillates 8 times. What is the height of the building? List T =? #cycles=8 oscillations t= 60 s L=?? (=height of building) T = time/# cycles T = 60 sec/8 cycles T = 7.5 sec

15. PROBLEM: A man wants to know the height of a building which has a pendulum hanging from its ceiling. He notices that in one minute the pendulum oscillates 8 times. What is the height of the building? List T = 7.5 sec #cycles=8 t= 60 s L=?? 7.5 2 = 4π 2 (L/9.8) 7.5 2 = 39.44 (L/9.8) 7.5 2 (9.8)= L 39.44 L = 14.7 m

16. Now you try a problem. The period of a simple pendulum is 2 seconds. Find its length. = 1 meter

17. A pendulum has a length of 3.0 m and executes 20. complete vibrations in 70. seconds. Find the acceleration of gravity at the location of the pendulum. Another problem

18. 1 st find the period A pendulum has a length of 3.0 m and executes 20. complete vibrations in 70. seconds. 1. f = cycles / seconds = 20 cycles / 70 seconds = 0.286 hz 2. T = 1 / f = 1 / 0.286 seconds = 3.5 seconds

19. Next find “g” Find the acceleration of gravity at the location of the pendulum. 3.5 s = 2π√(3.0/g) 3.5 s = 6.28 √(3.0/g) Square both sides 12.25 = 39.43 (3.0/g) 12.25 = 118.3/g 12.25(g) = 118.3 Divide by 12.25 g = 9.658 m/s/s T= 3.5 seconds Heads up!! If you ÷ by 2 π  Use (2 π ) !! g = 9.7 m/s/s