### Create a StudySoup account

#### Be part of our community, it's free to join!

Already have a StudySoup account? Login here

# week 10 short assignments 1220

Mizzou

GPA 3.0

### View Full Document

## About this Document

## 6

## 0

## Popular in College Physics II

## Popular in Physics 2

This 11 page Bundle was uploaded by Dragon Note on Friday April 15, 2016. The Bundle belongs to 1220 at University of Missouri - Columbia taught by Y Zhang in Spring 2016. Since its upload, it has received 6 views. For similar materials see College Physics II in Physics 2 at University of Missouri - Columbia.

## Reviews for week 10 short assignments

### What is Karma?

#### Karma is the currency of StudySoup.

#### You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 04/15/16

Short Assignment By 4/04/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Short Assignment By 4/04/2016 Due: 11:00am on Monday, April 4, 2016 To understand how points are awarded, read theg Policy for this assignment. Problem 28.48 Light with a wavelength of 623 passes through a slit 8.31 wide and falls on a screen 1.89away. Part A Find the distance on the screen from the central bright fringe to the third dark fringe above it. ANSWER: = 43.6 Correct Problem 28.66 A diffraction grating with 365 is 1.00 in front of a screen. Part A What is the wavelength of light whose first-order maxima will be 1from the central maximum on the screen? ANSWER: = 496 Correct Score Summary: Your score on this assignment is 100%. You received 2 out of a possible total of 2 points. Short Assignment by 4/06/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Short Assignment by 4/06/2016 Due: 11:00am on Wednesday, April 6, 2016 To understand how points are awarded, read theading Policy for this assignment. Gedanken Conceptual Questions Einstein developed much of his understanding of relativity through the use of gedanken, or thought, experiments. In a gedanken experiment, Einstein would imagine an experiment that could not be performed because of technological limitations, and so he would perform the experiment in his head. By analyzing the results of these experiments, he was led to a deeper understanding of his theory. In each the following gedanken experiments, Albert is in the exact center of a glass-sided freight car speeding to the right at a very high speed relative to you. Albert has a flashlight in each hand and directs them at the front and rear ends of the freight car. Albert switches the flashlights on at the same time. Part A In Albert's frame of reference, which beam of light travels at a greater speed, the one directed toward the front or the one toward the rear of the train, or do they travel at the same speed? Which beam travels faster in your frame of reference? Enter the answers for Albert's frame of reference and your frame of reference separated by a comma using the terms front, rear, and same. For example, if in Albert's frame of reference the beam of light directed toward the front of the train travels at a greater speed and in your frame of reference the two beams travel at the same speed, then enter front,same. Hint 1. A postulate of Einstein’s relativity One of the basic postulates of special relativity is that the speed of light is the same for all observers, regardless of the speed of either the observer or the source of the light. ANSWER: Correct Part B In Albert's frame of reference, which end, front or rear, is struck by light first, or are they struck at the same time? Which end is struck first in your frame of reference? Enter the answer for Albert's frame of reference and your frame of reference separated by a comma using the terms front, rear, and same. For example, if in Albert's frame of reference the beam of light strikes the front first and in your frame of reference the two beams strike at the same time, then enter front,same. Hint 1. Distinguishing between frames of reference It is important to clearly distinguish between the two frames of reference involved in this problem. In Albert’s frame, the train is at rest. Albert, the flashlights, the walls, and the ceiling and floor of the train are all completely stationary in this frame of reference. In your frame of reference, the train and everything in it is moving. Albert, the flashlights, the walls, and the ceiling and floor of the train are all moving at exactly the same speed in your frame Short Assignment by 4/06/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... of reference. Hint 2. Situation in Albert’s frame In Albert’s frame, the train is completely at rest. The light from the flashlights is emitted directly between the two stationary ends, and one beam moves to the right and the other moves to the left at exactly the same speed, the speed of light. Hint 3. Situation in your frame In your frame, both the front and rear ends are moving to the right at the same constant speed. The light from the flashlights is emitted directly between these two moving ends, and one beam moves to the right and the other moves to the left at exactly the same speed, the speed of light. ANSWER: Correct One of the most startling consequences of special relativity is that two events can be simultaneous for one observer, in one frame of reference, but may not be simultaneous for a different observer in a different frame. Thus, saying that two things "happened at the same time" may be true for one person and false for another, but both observers are correct in their statements. Short Assignment by 4/06/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Now Albert directs his flashlights at the ceiling and floor of the freight car. The flashlights are located midway between the ceiling and the floor and Albert switches them on at the same time Part C In Albert's frame of reference, which surface, ceiling or floor, is struck by light first, or are they struck at the same time? Which surface is struck first in your frame of reference? Enter the answer for Albert's frame of reference and your frame of reference separated by a comma using the terms ceiling, floor, and same. For example, if in Albert's frame of reference the ceiling is struck by light first and in your frame of reference the floor and the ceiling are struck by light at the same time, then enter ceiling,same. Hint 1. Situation in Albert's frame In Albert’s frame, the train is completely at rest. The light from the flashlights is emitted directly between the floor and the ceiling, and one beam moves up and the other moves down at exactly the same speed, the speed of light. Hint 2. Situation in your frame In your frame, the entire train is moving to the right, but no part of the train is moving vertically. The light from the flashlights is emitted directly between the floor and the ceiling, and one beam moves up and the other moves down at exactly the same speed, the speed of light. Short Assignment by 4/06/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... ANSWER: Correct Albert is playing laser tag in the freight car. Two "assassins" sneak into the freight car with Albert. One is positioned against the front end and the other against the rear end. They each fire a laser at Albert. The two lasers strike Albert at the same time. Part D In Albert's frame of reference, who fired first, the person against the rear end or the person against the front end, or did they fire at the same time? In your frame of reference, who fired first? Enter the answers for Albert's frame of reference and your frame of reference separated by a comma using the terms front, rear, and same. For example, if in Albert's frame of reference the person against the front end fired first and in your frame of reference both "assassins" fired at the same time, then enter front,same. Hint 1. Situation in Albert's frame In Albert’s frame, the train is completely at rest. The two assassins are equally distant from Albert and their laser beams travel at equal speeds. Hint 2. Situation in your frame In your frame, Albert is directly between the assassins and moving to the right. The rear laser beam moves to the right at the speed of light and the front laser beam moves to the left at the speed of light. Short Assignment by 4/06/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Therefore, Albert is moving in the same direction as the rear beam and in the opposite direction of the front beam. Which beam will take a larger amount of time to hit Albert? ANSWER: front rear ANSWER: Correct This is another example of how two events, the firing of the lasers, can be simultaneous in one frame of reference and not simultaneous in another frame. Score Summary: Your score on this assignment is 100%. You received 1 out of a possible total of 1 points. Short Assignment by 4/08/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Short Assignment by 4/08/2016 Due: 11:00am on Friday, April 8, 2016 To understand how points are awarded, read theading Policy for this assignment. Problem 29.6 A neon sign in front of a cafe flashes on and off once every 4.2, as measured by the head cook. Part A How much time elapses between flashes of the sign as measured by an astronaut in a spaceship moving toward Earth at a speed of 0.82 ? Express your answer using two significant figures. ANSWER: = 7.3 All attempts used; correct answer displayed When Time Flies...It Runs More Slowly Learning Goal: To understand length contraction and time dilation. An inertial frame of reference is one in which Newton's laws hold. Any frame of reference that moves at a constant speed relative to an inertial frame of reference is also an inertial frame. The proper lengof an object is defined to be the length of the object as measured in the object's rest frame. If the length of the object is measured in any other inertial frame, moving with speed relative to the object's rest frame (in a direction paralle), the resulting lengthis given by the length contraction equation , where is the speed of light. Similarly, if two events occur at the same spatial point in a particular reference frame, and an observer at rest in this frame measures the time interval between these two events, the time interval so measured is defined to be the proper time . When the time interval is measured in any other inertial frame, again moving with speed relative to the first frame, the resulting time intervalis given by the time dilation equation . Part A Suppose that you measure the length of a spaceship, at rest relative to you, to be 400 . How long will you measure it to be if it flies past you at a speed of ? Express the length in meters to three significant figures. ANSWER: Short Assignment by 4/08/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... = 264.6 Correct Notice that this is smaller than the proper length of the spaceship. This is why the discrepancy between measurements of moving objects and their proper length is sometimes referred to as length contraction. Part B The spaceship from Part A has a large clock attached to its side. This clock ran at the same rate as your watch when you were in the same reference frame. How much time will pass on your watch as 80 passes on the clock attached to the ship? Express your answer in seconds to three significant figures. Hint 1. How to approach the problem You are given the amount of time that elapses as measured by the occupants of the spaceship. Assume that your frame is at rest and that the spaceship is moving toward you at a relative spee. ANSWER: = 120.9 Correct Notice that this is larger than the time measured on the ship. This is why the difference between measurements of moving objects and measurements of proper time is referred to as time dilation. Two spaceships, named A and B, are flying toward each other with relative speed . Part C If the captain of ship A fires a missile, counts 1on his watch, and then fires a second missile, how much time will the captain of ship B measure to have passed between the firing of the two missiles? Express your answer in seconds to three significant figures. Hint 1. How to approach the problem The proper time is the time interval measured by the captain of ship A; he is in the rest frame of the ship from which the missiles are fired. The captain of ship B sees ship A approaching at a speed of . This is the speed that will appear in the time dilation equation. ANSWER: = 16.7 Short Assignment by 4/08/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Correct Part D The captain of ship B knows that ship A uses 2-m-long missiles. She measures the length of the first missile, once it has finished accelerating, and finds it to be only 0.87long. What is the speed of the missile, relative to ship B? Express your answer in meters per second to three significant figures. Use . ANSWER: = Correct Rest Length and Length Contraction Ranking Task The graph below shows the value of the term as a function of velocity. Six spaceships with rest lengths zoom past an intergalactic speed trap. The officer on duty records the speed of each ship, . (No ship is going in excess of the stated speed limit of , so she doesn’t have to pull anyone over for a ticket.) Part A Rank these spaceships on the basis of their length measured by the police officer. Rank from largest to smallest. To rank items as equivalent, overlap them. Hint 1. Rest length versus "moving" length The rest length of each spaceship is given. The length measured by the police officer will be less than this amount because, in the police officer’s frame of reference, the ships are moving and will contract as the result of length contraction. Hint 2. The length contraction relation Short Assignment by 4/08/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... The mathematical relationship between the rest length of the spaceship ( ) and "moving" length ( ) is . ANSWER: Correct Part B Rank these spaceships on the basis of their length as measured by their respective captains. Rank from largest to smallest. To rank items as equivalent, overlap them. Hint 1. The captain’s frame of reference Relative to each ship's respective captain, sitting in the captain’s chair, each spaceship is at rest. This is true regardless of the speed of the ship relative to the police officer or anyone else. ANSWER: Short Assignment by 4/08/2016 https://session.masteringphysics.com/myct/assignmentPrintView?displ... Correct Score Summary: Your score on this assignment is 66.7%. You received 2 out of a possible total of 3 points.

### BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.

### You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

## Why people love StudySoup

#### "I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

#### "Selling my MCAT study guides and notes has been a great source of side revenue while I'm in school. Some months I'm making over $500! Plus, it makes me happy knowing that I'm helping future med students with their MCAT."

#### "Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

#### "It's a great way for students to improve their educational experience and it seemed like a product that everybody wants, so all the people participating are winning."

### Refund Policy

#### STUDYSOUP CANCELLATION POLICY

All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email support@studysoup.com

#### STUDYSOUP REFUND POLICY

StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here: support@studysoup.com

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to support@studysoup.com

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.