{"action":"opened","issue":{"url":"https://api.github.com/repos/ericmazur/PnPbook/issues/108","labels_url":"https://api.github.com/repos/ericmazur/PnPbook/issues/108/labels{/name}","comments_url":"https://api.github.com/repos/ericmazur/PnPbook/issues/108/comments","events_url":"https://api.github.com/repos/ericmazur/PnPbook/issues/108/events","html_url":"https://github.com/ericmazur/PnPbook/issues/108","id":109143496,"number":108,"title":"elevator woman : choice of reference frame","user":{"login":"JohnDenker","id":14043887,"avatar_url":"https://avatars.githubusercontent.com/u/14043887?v=3","gravatar_id":"","url":"https://api.github.com/users/JohnDenker","html_url":"https://github.com/JohnDenker","followers_url":"https://api.github.com/users/JohnDenker/followers","following_url":"https://api.github.com/users/JohnDenker/following{/other_user}","gists_url":"https://api.github.com/users/JohnDenker/gists{/gist_id}","starred_url":"https://api.github.com/users/JohnDenker/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/JohnDenker/subscriptions","organizations_url":"https://api.github.com/users/JohnDenker/orgs","repos_url":"https://api.github.com/users/JohnDenker/repos","events_url":"https://api.github.com/users/JohnDenker/events{/privacy}","received_events_url":"https://api.github.com/users/JohnDenker/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-09-30T17:43:12Z","updated_at":"2015-09-30T17:43:12Z","closed_at":null,"body":"See item #107 for a catalog of related issues.\r\n\r\nIn exercise 8.5 in section 8.5 on page 184 it says:\r\n> Even though she is at rest in the elevator, her acceleration is not zero because the elevator and she are both accelerating upward.\r\n\r\nIn accordance with the equivalence principle, it must be emphasized that there is a ***choice*** involved.  If you choose to use the terrestrial lab frame, you are free to do so ... but other folks remain free to choose differently.  It's a choice, not a law of physics.\r\n\r\nSpecific constructive suggestion:  Simple rewrite:\r\n>> Even though she is at rest in the elevator, her acceleration is not zero because we choose to analyze the situation relative to the terrestrial lab frame.  Relative to this frame, the elevator and she are both accelerating upward.  (Other ways of choosing the reference frame will be discussed in sections 13.3 and 13.4.)"}}