Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Newton's theorem of revolving orbits wikipedia , lookup
Classical mechanics wikipedia , lookup
Fictitious force wikipedia , lookup
Work (thermodynamics) wikipedia , lookup
Newton's laws of motion wikipedia , lookup
Fundamental interaction wikipedia , lookup
Centrifugal force wikipedia , lookup
SMDEP Physics Work, Power, Potential Energy New Syllabus • Available at front • Shifting topics by one day through “gravity”; one day less on gravity – NO HOMEWORK FOR WEDS! – Also, no TA session Weds • Andrew teaching WTh, MTu – KR available by email • Quiz on Friday Friday’s Mechanics Quiz • No calculators needed/allowed • No clickers needed • Don’t memorize formulas – Any formulas needed will be provided • Mostly qualitative, conceptual questions • Length: About 30 minutes • Material: Kinematics, Mechanics, Energy – Circular motion, friction, springs – NOT: vectors, dot products, momentum • Grades not instant • Also: Midcourse evaluations – What would you change about the course? Resources • Textbook: especially end-of-chapter “Questions” • New web site – http://www.astro.yale.edu/krines/smdep/ – Powerpoints of first two weeks, more to come • Email – KR: [email protected] – AC: [email protected] • Office hours: KR today 5-6 pm Marigolds Ch 8, #1: distance spring stretched 0.09 m 0.9 m 9m 90 m Other Didn’t finish 93% 2% ’t fin r id n th e 0% is h 0% O m 90 m 9 9 m 0% 0. 09 m 5% 0. 1. 2. 3. 4. 5. 6. Ch 8, #8: is air resistance conservative? Yes No Sometimes Didn’t finish 87% 13% ’t fin is h 0% id n m et im es So o N s 0% Ye 1. 2. 3. 4. • Normal forces – Always act at right angles to surface – Force of electron clouds repelling each other – Friction always normal to normal force, so friction is always parallel to surface • “Centrifugal forces” – NO! • “The centripetal force” – No • “A centripetal force” – Yes – Centripetal force is always exerted by something touching object or gravity: e.g., normal force from rollercoaster track, string/rope tension force, Earth’s gravity A stone is attached to a string is whirled in a vertical plane. Let T1, T2, T3, and T4 be the tensions required (at the locations shown) for the stone to have a constant speed v0 throughout. Which is true? ... on e of =. .. T2 =. .. N > T1 T3 = T2 >. .. 13% 10% 5% T3 T2 > T3 > T2 > T1 = T4 T3 = T2 = T1 = T4 T1 > T2 = T4 > T3 None of the above T3 1. 2. 3. 4. 73% T2 T4 T1 You are pushing a wooden crate across the floor at constant speed. You then turn the crate on end, reducing by half the surface area touching the floor. In the new orientation, to push the same crate across the same floor with the same speed, the force that you apply must be about: Four times greater Twice as great Equally great Half as great One-fourth as great 75% 14% 11% 0% ur tim es gr Tw e. ic .. e as gr Eq ea ua t lly gr H ea al fa O t ne s gr -fo ea ur t th as ... 0% Fo 1. 2. 3. 4. 5. Consider a person standing in an elevator that is accelerating upward. The upward normal force exerted by the elevator floor on the person is: 1. 2. 3. Larger than Equal to Smaller than ..the downward weight of the person You stand on a scale in your bathroom. It reads 150 lb. In which of the following situations will it read less? 1. 2. 3. 4. 5. In an elevator accelerating upward In an elevator accelerating downward In an elevator moving up at constant velocity In an elevator moving down at constant velocity Two of the above al f H as m e sa e Th 0 Twice The same as Half ..what it was before ic e 1. 2. 3. Tw 70 In the 17th century, Otto von Güricke, a physicist in Magdeburg, fitted two hollow bronze hemispheres together and removed the air from the resulting sphere with a pump. Two eight-horse teams could not pull the halves 33% 33% 33% apart even though the hemispheres fell apart when air was re-admitted. Suppose von Güricke had tied both teams of horses to one side and bolted the other side to a heavy tree trunk. In this case, the tension on the hemispheres would be: 10 Consider a weightlifter holding a 500 pound barbell stationary above his head. The weightlifter is doing: 86% 1. Positive work on the barbell 2. Negative work on the barbell 3. No work on the barbell 9% rb e ba th e on or k w o N at iv e eg N Po si tiv e w w or k or k on on th e th e ... ... ll 5%