p140w07_ct4 - circle is small i v r f v r f v r i v r v r r...

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Physics 140: Winter 2007 Lecture #4 January 16, 2007 Dave Winn Racquetball Striking a Wall Copyright: Loren M. Winters Mt. Etna Andrew Davidhazy
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A navy ship simultaneously fires two shells at enemy ships. The shells follow the parabolic trajectories shown in the diagram below. Which of the two enemy ships gets hit first? (Do not assume that the shells are fired with the same initial speed) 1. Ship A 2. Both at the same time 3. Ship B 4. Need more info to tell
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Another special 2D motion • Uniform circular motion, another special case of 2D motion • Object traveling at constant speed on a circle needs a force of fixed size, always to motion, to keep moving in a circle F r v r v r F r v r F r v r F r
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How large is the acceleration in circular motion? • We can tell just by examining the path • Acceleration is big when v is large or the
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Unformatted text preview: circle is small i v r f v r f v r i v r v r r v a t v a r s v v v v s t 2 = = = s Approximate circular motion Each part of every 2D path can be approximated by a part of a circle This lets you estimate the component of the acceleration Where it curves fast, r is small, and v 2 /r is large; when slow, its small r eff r eff Physics student Joe is watching his friend Sandy depart from the train station. As the train pulls out of the station at a constant speed, Sandy drops a farewell package out the window. Sandy sees the farewell package drop straight to the ground beneath her hand Joe sees the package moving to the right while it falls Who is correct? 1. Sandy 2. Joe 3. Both Sandy Joe...
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p140w07_ct4 - circle is small i v r f v r f v r i v r v r r...

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