LecturesWeek6

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: his roller coaster car rolls without friction. (a) What minimum kinetic energy does the car need in order to make it over the hill? (1/A) mgh (2/B) mgH (3/C) mg (H - h) (4/D) mg (H + h) (b) How much kinetic energy will the car then have when it reaches the bottom of the hill? (1/A) mgh (2/B) mgH (3/C) mg (H - h) (4/D) mg (H + h) m H ?!? h Ex. Assume that this roller coaster car rolls without friction. (a) What minimum kinetic energy does the car need in order to make it over the hill? (1/A) mgh (2/B) mgH (3/C) mg (H - h) (4/D) mg (H + h) (b) How much kinetic energy will the car then have when it reaches the bottom of the hill? (1/A) mgh (2/B) mgH (3/C) mg (H - h) (4/D) mg (H + h) m H ?!? h Ex. The potential energy U(r) for the interaction between a proton and nucleus is graphed as a function of their center-to-center separation r. (a) Which position r is a point of unstable equilibrium? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these fm (b) Which position r is a point of stable equilibrium? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these (c) At which position r is the force on the proton attractive? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these r Nucleus Proton Ex. The potential energy U(r) for the interaction between a proton and nucleus is graphed as a function of their center-to-center separation r. (a) Which position r is a point of unstable equilibrium? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these fm (b) Which position r is a point of stable equilibrium? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these (c) At which position r is the force on the proton attractive? (1/A) 1 fm (2/B) 3 fm (3/C) 4 fm (4/D) 7 fm (5/E) None of these r Nucleus Proton Ex. with Univ. Grav: Escape velocity It’s possible to escape the Earth......otherwise no NASA. Only because the force of gravity decreases with distance from the Earth. A nice illustration of energy ideas: What is the minimum speed necessary to get infinitely far away from the Earth? Result (transparency): vescape = √(2GM/R) Independent of the mass of the falling object. Meteor Reentry from Space: same as escape velocity Space Shuttle 1.2 km Meteor ~ 50 m dia. ~ 3 x 108 kg @ 13 km/s → 2.5 x 1016 J Barringer Meteor Crater (Arizona) Engraving of the 1833 Leonid Meteor Storm Power Power is the rate of doing work or transferring energy. Units: 1 Watt = Joule/sec Q: How much power does it take to hold a barbell over your head? A: None Q: How much power does it take to lift a barbell? A: It depends how fast you do it. : ￿ f ￿ f ￿ f dU...
View Full Document

This note was uploaded on 09/29/2012 for the course MATH 1920 taught by Professor Pantano during the Spring '06 term at Cornell University (Engineering School).

Ask a homework question - tutors are online