Physics 202: Lecture 8, Pg 1

Transcription

1 Physics 132: Review e Elements of Physics II Agenda for Today Review Physics 202: Lecture 8, Pg 1

2 4/20 Final Exam Office Hours (MP 129A): M 12-1pm T 1-3pm W 12-1pm R 10-12pm Review Sessions/Office Hours (MP 125A): Monday 4/18 1-3pm Tuesday 4/ pm 12 and 2-4 pm Physics 202: Lecture 8, Pg 2

3 Clicker Question 1: Which is an inertial reference frame (or at least a very good approximation of one)? A. A jet plane during takeoff. B. A jet plane flying straight and level at constant speed. C. A jet plane turning at constant speed. D. B and C. E. A, B, and C. Physics 202: Lecture 8, Pg 3

4 Clicker Question 2: A spaceship travels at a constant speed to a distant planet. If the trip takes 12 yrs according to clocks on the earth, and 9.2 years according to clocks on the ship, how far away is the planet (in the Earth frame)? (a) (b) (c) (d) (e) lightyears 8.95 lightyears 7.68 lightyears lightyears 12 lightyears Physics 202: Lecture 8, Pg 4

5 Clicker Question 2: A spaceship travels at a constant speed to a distant planet. If the trip takes 12 yrs according to clocks on the earth, and 9.2 years according to clocks on the ship, how far away is the planet? Physics 202: Lecture 8, Pg 5

6 Example Earth and Sun are 8.3 light minutes apart, as measured in their rest frame. What is the speed of a spacecraft that makes the trip in 5.0 min according to its on-board clocks? Physics 202: Lecture 8, Pg 6

7 Clicker Question 3: A firecracker explodes high overhead. You notice a slight delay between seeing the flash and hearing the boom. At what ttime does the event t firecracker explodes occur in your reference frame? A. At the instant you hear the boom. B. At the instant you see the flash. C. Very slightly before you see the flash. D. Very slightly after you see the flash. E. There s no unique answer because it depends on the observer. Physics 202: Lecture 8, Pg 7

8 Clicker Question 3.5: A tree and a pole are 3000 m apart. Each is hit by a bolt of lightning. Mark, who is standing at rest midway between the two, sees the two lightning bolts at the same time. Nancy is flying her rocket at v = 0.5 c in the direction from the tree to the pole. The lightning hits the tree just as she is passing it. Define event 1 to be lightning strikes tree and event 2 to be lightning strikes pole. For Nancy, does event 1 occur (a) before, (b) after, (c) or at the same time as event 2? Physics 202: Lecture 8, Pg 8

9 Clicker Question 3.5: 9 Physics 202: Lecture 8, Pg 9

10 Clicker Question 3.5 : Nancy s Frame Flashes reach Mark at the same 10 Physics time202: Lecture 8, Pg 10

11 Clicker Question 4: Peggy passes Ryan at velocity v. Peggy and Ryan both measure the time it takes the railroad car, from one end to the other, to pass Ryan. The time interval Peggy measures is the time interval Ryan measures. A. longer than B. at the same as C. shorter than Physics 202: Lecture 8, Pg 11

12 Clicker Question 5: Peggy passes Ryan at velocity v. Peggy and Ryan both measure the length of the railroad car, from one end to the other. The length Peggy measures is the length Ryan measures. A. longer than B. at the same as C. shorter than Physics 202: Lecture 8, Pg 12

13 Example Physics 202: Lecture 8, Pg 13

14 Clicker 6: The image produced by a concave mirror of a real object is: A. Always Real B. Always Virtual C. Sometimes Real, Sometimes Virtual Concave mirror: f > 0 Real Object means in front of mirror: d o > 0 Mirror Equation: d o d i f d i can be negative or positive! 1 d d i 1 f 1 d d 0 Physics 202: Lecture 8, Pg 14

15 Clicker Question 7: A lens creates an image as shown. In this situation, the object distance s is A. Larger than the focal length f. B. Equal to the focal length f. C. Smaller than focal length f. Physics 202: Lecture 8, Pg 15

16 Example A screen 1.0 m wide is located.2.0 m from a pair of slits illuminated by 633 nm laser light, with its center on the centerline of the slits. Find the highest-order bright fringe that will appear on the screen if the slit spacing is 0.10 mm. Physics 202: Lecture 8, Pg 16

17 Clicker Question 8: A nuclear bomb releases roughly J when it explodes. About how much mass is lost during the explosion? (a) 5.6 grams (b) 5.6 kg (c) 560 kg (d) kg (e) kg Physics 202: Lecture 8, Pg 17

18 Clicker Question 9: A circular loop of radius r = 5 cm and resistance R = 010Ω 0.10 Ω is in a region where there is a uniform magnetic field in the direction shown in the figure that increases linearly with time according to the expression B(t) = B 0 t / τ with B 0 = 0.5 T and t = 100 s. (The loop is stationary.) What direction will current flow in the loop? (a) (b) Physics 202: Lecture 8, Pg 18

19 Clicker Question 10: A conducting metal band containing a 5 Ω resistor is formed into a circle of radius R as shown in the diagram. The computer-controlled screw drive turns so as to decrease the circumference of the loop. Because of this a current flows: (a) CW (b) CCW Physics 202: Lecture 8, Pg 19

20 What is the sign of q? Clicker Question 11: (a) positive (b) negative (c) need more information Physics 202: Lecture 8, Pg 20

21 Clicker Question 12: What is the magnitude of the current I 2? Assume R 1 = 1, R 2 = 2, R 3 = 3, 1 = 15 V and 2 = 9 V. a) 200 ma b) 500 ma c) 1 A d) 2 A e) 3A Physics 202: Lecture 8, Pg 21

22 Clicker Question 12: What is the magnitude of the current I 2? Assume R 1 = 1, R 2 = 2, R 3 = 3, 1 = 15 V and 2 = 9V V. Physics 202: Lecture 8, Pg 22

23 Clicker Question 13: As in lecture, a cylindrical magnet is released to fall through a narrow copper pipe. Assume, as shown, that it is dropped with the north pole closer to the ground. The tube is at rest. An induced current flows in the direction indicated by the arrow (T) True (F) False Physics 202: Lecture 8, Pg 23

24 Clicker Question 14: A charged particle is traveling at speed v. It encounters a static magnetic field oriented perpendicular to its path. The particle changes its (a) speed ( = magnitude of the velocity). (b) direction. (c) both its speed and direction. (d) neither its speed or direction. (e) All of the above scenarios are possible. Physics 202: Lecture 8, Pg 24

25 Clicker Question 15: The trajectory of the particle is best described as (a) (b) (c) a helix. a circle oriented in the plane of the page. a circle oriented perpendicular to the page. Physics 202: Lecture 8, Pg 25

26 Clicker Question 16: Three particles of the same charge and the same speed of v, but with three different masses, enter a region of constant magnetic field into the page (B = 0.5 T) A uniform electric field is now applied in the region of the magnetic field so that particles continue to move up vertically without bending. What should be the direction of this electric field? (a) (b) (c) (d) (e) right left up down into the page Physics 202: Lecture 8, Pg 26

27 Clicker Question 17: The circuit below contains two identical light bulbs. If light bulb B was replaced by a light bulb of twice the resistance, what would happen to light bulb A? a) Get dimmer b) Get brighter c) Go out d) Stay the same e) Not enough information Physics 202: Lecture 8, Pg 27

28 Clicker Question 18: The image below shows two regions with electric fields as labeled. Which point has the highest electric potential? Assume there are no other fields. a) A b) B c) C d) Cannot be determined Physics 202: Lecture 8, Pg 28