Physics Help Forum A question regarding vectors and angle between vectors

 Physics Physics Forum - General Physics Discussion and Physics News

 Nov 8th 2018, 12:06 AM #1 Junior Member   Join Date: Nov 2018 Posts: 1 A question regarding vectors and angle between vectors In my attempt, I got 2 answers √3 and 1 but the solutions say that the answer is only √3. Am I missing something? Sent from my S6 using Tapatalk
 Nov 9th 2018, 04:45 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 Consider the first equation you are given: $| \hat A \times \hat B | = - \sqrt 3 \ \hat A \cdot \hat B$ The left hand side is a positive number, since it's a magnitude. Therefore the right hand side must also be positive, which means $\hat A \cdot \hat B$ must be negative. This rules out the possibility that theta = -60 degrees. topsquark likes this.
Nov 11th 2018, 01:30 PM   #3
Physics Team

Join Date: Apr 2009
Location: Boston's North Shore
Posts: 1,576
 Originally Posted by ChipB Consider the first equation you are given: $| \hat A \times \hat B | = - \sqrt 3 \ \hat A \cdot \hat B$
That expression is not in the paper he posted. The cross product is defined for two vectors whose magnitude does not appear explicitly in the expression defining it;.

Nov 11th 2018, 02:59 PM   #4
Physics Team

Join Date: Jun 2010
Location: Morristown, NJ USA
Posts: 2,354
 Originally Posted by Pmb That expression is not in the paper he posted.
?? It’s the very first line of the photo the OP posted from his text with the problem statement - are you not seeing it?

Last edited by ChipB; Nov 11th 2018 at 03:02 PM.

 Tags angle, question, vectors

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post princess44725 Kinematics and Dynamics 2 Jun 29th 2012 08:00 PM Sterlingm Kinematics and Dynamics 1 Jun 27th 2010 12:20 PM decoy808 Kinematics and Dynamics 2 Nov 24th 2009 05:17 PM KaylaN Kinematics and Dynamics 2 Sep 22nd 2009 08:31 AM Ralph4christ Kinematics and Dynamics 7 May 31st 2009 10:43 AM