Cosmology and Quantum Introduction solutions

Cosmology and Quantum Introduction solutions - PHYSICS 6...

Info icon This preview shows pages 1–2. Sign up to view the full content.

PHYSICS 6 SPRING 2006 HOMEWORK 3 SOLUTIONS 1. The charged pion ( π + ) decays has an average decay time of 2.6x10 -8 sec. a. If a π + is travelling in a lab at 0.9999c what is its average decay time? b. How far does it travel before decaying (on the average)? d=vt = 3x10 8 × 1.8x10 -6 = 5.4x10 2 m c. The π + turns into three particles (usually muon and 2 neutrinos) when it decays. Suppose the muon is produced along the direction of the π + motion and has a velocity of 0.99c in the π + rest frame. What is the muon velocity in the lab? In π + rest frame (S ) muon has u = 0.99c, but π + is moving at V=0.9999c in lab frame (S). Then 2. Judy and Andy are twins. Judy gets on a rocket that goes to a star system 20 light years away from earth (as measured from earth, i.e. Andy's frame of reference). a. She travels at 0.8c. How many years does it take her to reach the star according to Andy? t= 20 c yr / 0.8 c = 25 yr b. What will Judy's clock read when she reaches the star? Judy's clock runs slow according to Andy, via t(Judy)= 25 × (1-0.8 2 )= 25 × (1-0.64) = 25 × (0.36)= 25 × 0.6 = 15 yr c.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern