Physics Help Forum AP Exam Booklet problem

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 Apr 23rd 2017, 08:17 PM #1 Junior Member   Join Date: Apr 2017 Posts: 1 AP Exam Booklet problem My head is severely broken right now. Maybe I have never been taught this or I'm just an idiot and don't remember. In the image that I clipped onto this thread I have a hard time understanding the last part where mb= (0.5kg) (7/3-1). Where does the -1 come from and why does it go in the parentheses with the 7/3. I understand how to get to (0.5kg)(7/3)=(0.5kg + mb) but how does that turn into the last part of the problem? Please I need help Attached Thumbnails   Last edited by DaveyBoySmith; Apr 23rd 2017 at 08:23 PM.
 Apr 24th 2017, 03:45 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,299 Starting with: 0.5 kg (7/3) = 0.5 kg + mb Subtract 0.5 kg from both sides: 0.5 kg (7/3) - 0.5 Kg = 0.5 kg + mb - 0.5 kg 0.5 kg (7/3) - 0.5 kg = mb Now apply the distributive property to the left hand side; recall that a(b+c) = ab + ac. In this case a =0.5 kg, b= 7/3, and c= -1: 0.5 kg (7/3) - 0.5 kg = 0.5 kg (7/3) + 0.5 kg (-1) = 0.5 kg (7/3-1) Hence 0.5 kg(7/3-1) = mb

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