High school Grade 12 vectors

In summary, the conversation is about a student struggling with a math homework question and seeking help. They share the question and their attempt at solving it, but are confused about the incorrect answer they received. Through the conversation, it is pointed out that the student made a mistake with the components of one of the given vectors and also incorrectly added 180 degrees to their angle. Eventually, the student realizes that they had the correct answer all along and it was just rounded differently in the book.
  • #1
Last chance U
10
0

Homework Statement



Hi, for some reason I can't post my homework question (Grade 12 math)


How do i fix this?

Here's my homework question






Homework Statement



In Exercises 15-30, add the given vectors by using the trigonometric functions and the Pythagorean theorem

19. A = 9.821,θA = 34.27
B = 17.45,θB = 752.50

Homework Equations



R=√Rx2+Ry2=

θ=tan-1 Ry/Rx =

The Attempt at a Solution




So here's what I did. I copied exactly what my teacher did but, when I checked the answer at the back of the book, the answer was wrong =(. Can you guys point out how I'm not getting the correct answer? thanks.


Here's what I have so far

19.

x component y component

Ax= 9.821cos34.27 Ay=9.821sin34.27
= 8.116 =5.530

Bx=17.45cos752.50 By=17.45cos752.50
= 14.72 =14.72



=22.84 =20.25

R=√22.84(2) + 20.25(2)= 30.52


θ=tan-1 20.25/22.84=41.56

θ=180+41.56




EDIT IT SAYS IN THE BOOK THAT THE ANSWERS ARE

R=27.27, θ=33.14
 
Last edited:
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  • #2
Why have you added 180 degrees to your angle?

Note that BOTH of your vectors lie in the first quadrant, so their sum must lie there as well.
 
  • #3
arildno said:
Why have you added 180 degrees to your angle?

Note that BOTH of your vectors lie in the first quadrant, so their sum must lie there as well.

?

I don't get it =(
 
  • #4
Last chance U said:
?

I don't get it =(

Both of your given vectors point to the northeast, so their sum must also point to the northeast. When you added 180 degrees to the angle you forced your vector to point to the southwest. Why would you do that?
 
  • #5
Last chance U said:

Homework Statement



Hi, for some reason I can't post my homework question (Grade 12 math)


How do i fix this?

Here's my homework question






Homework Statement



In Exercises 15-30, add the given vectors by using the trigonometric functions and the Pythagorean theorem

19. A = 9.821,θA = 34.27
B = 17.45,θB = 752.50

Homework Equations



R=√Rx2+Ry2=

θ=tan-1 Ry/Rx =

The Attempt at a Solution




So here's what I did. I copied exactly what my teacher did but, when I checked the answer at the back of the book, the answer was wrong =(. Can you guys point out how I'm not getting the correct answer? thanks.


Here's what I have so far

19.

x component y component

Ax= 9.821cos34.27 Ay=9.821sin34.27
= 8.116 =5.530

Bx=17.45cos752.50 By=17.45cos752.50
= 14.72 =14.72
Your components for ##\vec{B}## are wrong. They shouldn't be equal.

=22.84 =20.25

R=√22.84(2) + 20.25(2)= 30.52


θ=tan-1 20.25/22.84=41.56

θ=180+41.56
Even with your incorrect numbers, both components of ##\vec{R}## are positive, so you should expect the angle to be between 0° and 90°, which is what you got from the arctangent function. So why did you add 180° to your result?

EDIT IT SAYS IN THE BOOK THAT THE ANSWERS ARE

R=27.27, θ=33.14
 
  • #6
Update guys, I have actually had the right the answer the whole time rofl. The book just rounded it differently lol. Thanks for the help though.
 

1. What are vectors in high school Grade 12?

Vectors in high school Grade 12 refer to a mathematical concept used to represent quantities that have both magnitude and direction. They are often represented as arrows on a graph and are commonly used in physics and engineering.

2. How are vectors used in high school Grade 12?

Vectors are used in high school Grade 12 to solve problems involving displacement, velocity, acceleration, and force. They can also be used to analyze motion and forces in two or three dimensions.

3. What is the difference between a scalar and a vector in high school Grade 12?

A scalar is a quantity that has only magnitude, while a vector has both magnitude and direction. Examples of scalars include temperature and mass, while examples of vectors include displacement and velocity.

4. How do you add and subtract vectors in high school Grade 12?

To add or subtract vectors in high school Grade 12, you must first break them down into their horizontal and vertical components. Then, you can add or subtract the components separately to get the resultant vector.

5. What is the importance of vectors in high school Grade 12?

Vectors are important in high school Grade 12 because they provide a way to analyze and solve problems involving quantities with both magnitude and direction. They are also used in many real-world applications, making them a valuable tool for understanding and solving complex problems.

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