{"action":"created","issue":{"url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/132","labels_url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/132/labels{/name}","comments_url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/132/comments","events_url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/132/events","html_url":"https://github.com/phetsims/forces-and-motion-basics/issues/132","id":87563887,"number":132,"title":"Why does g=10.0?","user":{"login":"samreid","id":679486,"avatar_url":"https://avatars.githubusercontent.com/u/679486?v=3","gravatar_id":"","url":"https://api.github.com/users/samreid","html_url":"https://github.com/samreid","followers_url":"https://api.github.com/users/samreid/followers","following_url":"https://api.github.com/users/samreid/following{/other_user}","gists_url":"https://api.github.com/users/samreid/gists{/gist_id}","starred_url":"https://api.github.com/users/samreid/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/samreid/subscriptions","organizations_url":"https://api.github.com/users/samreid/orgs","repos_url":"https://api.github.com/users/samreid/repos","events_url":"https://api.github.com/users/samreid/events{/privacy}","received_events_url":"https://api.github.com/users/samreid/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/labels/Summer%202015%20redeploy","name":"Summer 2015 redeploy","color":"5319e7"}],"state":"closed","locked":false,"assignee":{"login":"ariel-phet","id":4051174,"avatar_url":"https://avatars.githubusercontent.com/u/4051174?v=3","gravatar_id":"","url":"https://api.github.com/users/ariel-phet","html_url":"https://github.com/ariel-phet","followers_url":"https://api.github.com/users/ariel-phet/followers","following_url":"https://api.github.com/users/ariel-phet/following{/other_user}","gists_url":"https://api.github.com/users/ariel-phet/gists{/gist_id}","starred_url":"https://api.github.com/users/ariel-phet/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ariel-phet/subscriptions","organizations_url":"https://api.github.com/users/ariel-phet/orgs","repos_url":"https://api.github.com/users/ariel-phet/repos","events_url":"https://api.github.com/users/ariel-phet/events{/privacy}","received_events_url":"https://api.github.com/users/ariel-phet/received_events","type":"User","site_admin":false},"milestone":null,"comments":2,"created_at":"2015-06-12T01:11:21Z","updated_at":"2015-06-13T01:36:18Z","closed_at":"2015-06-13T01:36:18Z","body":"I noticed this code:\r\n\r\n```js\r\n    //Returns the friction force on an object given the applied force\r\n    getFrictionForce: function( appliedForce ) {\r\n      \r\n      // TODO: Why does g=10.0?\r\n      var g = 10.0;\r\n      var sum = function( a, b ) {return a + b;};\r\n      var toMass = function( item ) {return item.mass;};\r\n      var mass = this.stack.map( toMass ).reduce( 0, sum );\r\n      var frictionForceMagnitude = Math.abs( this.friction * mass * g );\r\n```\r\n\r\n(I just added the TODO).  Why is g=10.0 and not something like 9.8?  @ariel-phet can you comment or delegate?"},"comment":{"url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/comments/111651602","html_url":"https://github.com/phetsims/forces-and-motion-basics/issues/132#issuecomment-111651602","issue_url":"https://api.github.com/repos/phetsims/forces-and-motion-basics/issues/132","id":111651602,"user":{"login":"ariel-phet","id":4051174,"avatar_url":"https://avatars.githubusercontent.com/u/4051174?v=3","gravatar_id":"","url":"https://api.github.com/users/ariel-phet","html_url":"https://github.com/ariel-phet","followers_url":"https://api.github.com/users/ariel-phet/followers","following_url":"https://api.github.com/users/ariel-phet/following{/other_user}","gists_url":"https://api.github.com/users/ariel-phet/gists{/gist_id}","starred_url":"https://api.github.com/users/ariel-phet/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ariel-phet/subscriptions","organizations_url":"https://api.github.com/users/ariel-phet/orgs","repos_url":"https://api.github.com/users/ariel-phet/repos","events_url":"https://api.github.com/users/ariel-phet/events{/privacy}","received_events_url":"https://api.github.com/users/ariel-phet/received_events","type":"User","site_admin":false},"created_at":"2015-06-13T01:36:18Z","updated_at":"2015-06-13T01:36:18Z","body":"I think this is definitely a \"if it ain't broke don't fix it\" scenario. g=10.0 is perfectly reasonable for this model, and as I said, since we do not reveal the value of the coefficients of friction to the user, there is no need to change it in this case. "}}