May 26th, 2012, 10:44 PM  #21 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs  Re: I have 2 questions please help !
The original problem gave the angular displacement in radians, but now you have revolutions. Which is it? (this would only affect the units, not the magnitudes) What answers did the teacher give? The provided diagram bears out the answers I gave. 
May 26th, 2012, 10:51 PM  #22 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
I don't know what he mean ? Segment #2 Constant velocity>8 secs > 100reve. Constant velocity? Equation? Segment #1 Constant acceleration >10 secs > 200 rev. Equation? or he meant another soving ? 
May 26th, 2012, 11:00 PM  #23 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs  Re: I have 2 questions please help !
Using your diagram, we have: The area of the trapezoid: The area of the rectangle: Hence: and so: These are the same answers I gave before. 
May 27th, 2012, 01:35 AM  #24 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
hhhhhhhhhh yes same answer ... thanks Dr.markl

May 27th, 2012, 02:08 AM  #25 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
thanks sou much

May 27th, 2012, 04:22 AM  #26 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
I am sorry to come agine here but I have Q 200 = 10 w0 + 50 a 200 = Q 12.5 = W0 + 10 a w = 12.5 now How at the final of solving you add ( Q + w ) to get I mean here " we now multiply the first equation by 2, then add the equations" How we can after that add if Q diifrent from w .. it'a this possible and how ?" 
May 27th, 2012, 10:37 AM  #27 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
sir In your solving you wrote this two equation 20 = w0 + 20a ====== 1 12.5 = W0 + 10 a ====== 2  as know 20 = Q and 12.5 w how can add this and we know that is w not equal to Q If it possible tell please why ? 
May 27th, 2012, 10:43 AM  #28 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs  Re: I have 2 questions please help !
We may add 2 equations because they are equations. If two quantities are equal, then we may add 1 quantity to one side of another equation and the other quantity to the other side since they are equal (we are adding the same thing to both sides of an equation, and so the equality must still hold). If we have: then we know: and 
May 27th, 2012, 11:46 AM  #29 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: I have 2 questions please help !
thaaaaaaaaanks new ideas I will keep it in my mind


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