
Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
A homework assignment from the physics 131 course at lafayette college, issued on april 15, 2009. It includes four problems covering various topics such as stellar collapse, rotation periods, vector calculus, and colliding objects. Students are expected to solve the problems individually and submit their answers by the due date.
Typology: Assignments
1 / 1
This page cannot be seen from the preview
Don't miss anything!
April 15, 2009
Physics 131 Level II Homework Set Section 1
You may discuss these problems with one or two other students (or with your instructor), but your final solutions should be written out by you alone. Under no circumstances should you see another student’s written solutions. If you have discussed these problems with anyone you must acknowledge the collaboration at the beginning of the corresponding problem. Homework is due in my office by 3:30 PM on the due date and solutions will then be made available on the course web site. No homework will be accepted after this time.
You are expected to carefully explain how, starting from basic principles, you have arrived at your answers. Please do not use paper with edges frayed from being ripped out of a spiral bound notebook. If the papers are illegible or disorganized, we reserve the right to return these papers without being graded. Unless instructed otherwise, all answers should be correct to 3 or 4 sig. figs.
Assignment 11: Due Monday, April 20, 2009
Problem 1: Consider a star that has a mass of 27 solar masses and a radius that is twice the solar radius. Assume that the star has a rotation period of 30 days. Suppose that this star under- goes a supernova event causing it to collapse to a neutron star with a radius of 25 km and retain- ing all of its mass (It actually retains only about 10% of its mass, but this makes the calculation much more difficult. Assume (not realistic) that the mass is uniformly spread throughout the body, both before and after. What is the new rotation period. Actually rotation periods for a neu- tron star can be as small as a few milliseconds (but can be much larger). How realistic is your value?
Problem 2: What must be the rotation speed of the Earth in order that it would begin to fly apart? Assume that the only force holding it together is the gravitational force.
Problem 3: Consider the vector AA = 4ˆ i + 9 ˆ j + 5 ˆ k and the vector BB = 3ˆ i + 4 ˆ j − 7 ˆ k. If the vector CC = AA × BB , find CC.
Problem 4: Two skaters each with mass m and speed v are headed towards each other along parallel paths separated by some distance D. As they pass each other, they stretch out their arms and grab each others hands and hold tight. The result is that they spin in a circle of diameter D. Find the final angular speed of the two skaters. What fraction of the initial kinetic energy is lost in this ignore the mass of their arms.