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PHY183-Lecture05

# PHY183-Lecture05 - Physics for Scientists& Physics for...

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Unformatted text preview: Physics for Scientists & Physics for Scientists & Engineers 1 Engineers 1 Physics for Scientists & Physics for Scientists & Engineers 1 Engineers 1 January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 1 Spring Semester 2011 Lecture 5 Clicker Quiz Clicker Quiz Clicker Quiz Clicker Quiz s An example of one dimensional motion with non-zero constant acceleration is A. NASCAR racing B. x = x + v t C. Free fall D. None of the above January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 2 Free Fall Free Fall Free Fall Free Fall s Near the surface of the Earth the acceleration due to the force of gravity is constant and is always in the downward direction s Free fall is an example of motion in one dimension with constant acceleration s So we can apply the five kinematic equations we derived yesterday using the vertical direction ( y-axis) with a = a y = - g • g = 9.81 m/s 2 January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 3 Free Fall Free Fall Free Fall Free Fall 2 2 , 9.81 m/s 1 2 = = - = = + + = + y y y a a g g y y v t at y y v t January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 4 ( 29 ( 29 2 2 1 2 2 = + = + = +- y y y y y y y v v at v v v v v a y y Measurement of Measurement of g Measurement of Measurement of g s Let’s test the assumption of constant gravitational acceleration s Take a computer to the top of the Wharton Center arking ramp and release it January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 5 parking ramp and release it from rest from a height of 12.7 m above the ground s Use a video camera to record the fall Measurement of Measurement of g (2) (2) Measurement of Measurement of g (2) (2) s The video frames give us the time calibration s The yellow line represents the equation ( 29 2 2 1 12.7 m + 9.81 m/s 2 y t =- January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 6 Free Fall Free Fall Free Fall Free Fall s We observe that heavy objects fall faster than light objects s This difference arises because of friction s Our free fall equations assume no friction s Here is a video from Apollo 15 of Commander David Scott dropping a 1.32 aluminum geological hammer and a 0.03 kg falcon feather on the surface of the Moon, August 2, 1971 s There is no atmosphere on the Moon so there is no friction January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 7 The Hammer and the Feather The Hammer and the Feather The Hammer and the Feather The Hammer and the Feather January 21, 2011 P h y s i c s f o r S c i e n t i s t s & E n g i n e e r s 1 8 Clicker Quiz Clicker Quiz Clicker Quiz Clicker Quiz s In the video, the hammer and feather drop a distance of 1.60 m in 1.41 s. What is the acceleration of gravity on the surface of the...
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PHY183-Lecture05 - Physics for Scientists& Physics for...

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