Question
If a galaxy is 500 Mly away from us, how fast do we expect it to be moving and in what direction?
Question by OpenStax is licensed under CC BY 4.0
Final Answer

1.0×104 km/s1.0\times 10^{4} \textrm{ km/s}

Solution video

OpenStax College Physics for AP® Courses, Chapter 34, Problem 4 (Problems & Exercises)

OpenStax College Physics Answers, Chapter 34, Problem 4 video poster image.

In order to watch this solution you need to have a subscription.

Start free trial Log in
vote with a rating of votes with an average rating of .
0 views

Calculator Screenshots

  • OpenStax College Physics, Chapter 34, Problem 4 (PE) calculator screenshot 1
Video Transcript
This is College Physics Answers with Shaun Dychko. Hubble discovered that the velocity with which another galaxy is receding away from us is approximately equal to this Hubble constant times the distance from us to the galaxy. We are told that the galaxy is 500 megalight years away and the Hubble constant is 20 kilometers per second per megalight year. So we multiply 20 by 500, the megalight years cancel leaving us with units of kilometers per second and that is 1.0 times 10 to the 4 kilometers per second away from us is the speed of the galaxy.