Physics Help Forum motion along a line

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

Sep 7th 2010, 07:44 PM   #1
Junior Member

Join Date: Sep 2010
Posts: 9
motion along a line

Hello,

I'm working on this problem:

 Select all the correct answers. A particle moving along a straight line is increasing its speed ifits velocity v is positive. its acceleration a is positive Both a>0 and v>0. Both a<0 and v<0.
I know that an object is speeding up if and only if v and a point in the same direction. So, I think the answer would be the last two, e.g.,

 Both a>0 and v>0. Both a<0 and v<0.
Is this correct?

 Sep 8th 2010, 09:35 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 Yes, you are correct. However the question is poorly worderd - I assume that what they meant to as is: "A particle moving along a straight line must be increasing its speed if ..." Certainly answers a and b could apply to a particle that is increasing its speed, but they may also apply to particles that are decreasing their speed as well.

 Tags line, motion

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