Why Is My Calculation of the Scalar Product Incorrect?

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SUMMARY

The calculation of the scalar product for the given vectors A and B was incorrectly performed due to a misunderstanding of the angle between the vectors. Vector A, with a magnitude of 3.60m, is oriented 70 degrees north of east, while Vector B, with a magnitude of 2.40m, is oriented 30 degrees south of west. The correct angle to use in the dot product formula, which is ABcosθ, must be determined accurately by drawing a diagram. The incorrect angle of -100 degrees led to an erroneous result, as the correct scalar product is not 13.00.

PREREQUISITES
  • Understanding of vector representation and orientation
  • Familiarity with the dot product formula: ABcosθ
  • Basic trigonometry, including cosine functions
  • Ability to visualize angles in a coordinate system
NEXT STEPS
  • Learn how to accurately determine angles between vectors using diagrams
  • Study vector addition and subtraction to understand vector orientation
  • Explore the concept of scalar and vector products in physics
  • Practice problems involving the dot product with varying vector orientations
USEFUL FOR

Students studying physics or mathematics, particularly those focusing on vector analysis and scalar products, will benefit from this discussion.

elpermic
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Homework Statement


Find the scalar product of the 2 vectors.
Vector A is north of east at 70 degrees with a magnitude of 3.60m
Vector B is south of west at 30 degrees with a magnitude of 2.40m

Homework Equations


ABcosx

The Attempt at a Solution


I did dot product using the formula, 3.60x2.40xcos(-100) and got the wrong answer.. The answer is 13.00. What the hell did I do wrong? I did as the formula said I should do and failed. I don't get it??
 
Last edited:
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elpermic said:
Vector A is north of east at 70 degrees …
Vector B is south of west at 30 degrees …

I did dot product using the formula, 3.60x2.40xcos(-100) …

Hi elpermic! :smile:

It ain't 100. :wink:​
 
elpermic said:
I did dot product using the formula, 3.60x2.40xcos(-100) and got the wrong answer.. The answer is 13.00.
(1) The formula calls for the angle between the two vectors. That angle is not 100°. (Draw a diagram.)
(2) The answer cannot be 13.
 

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