Little help with some simple Vector physics

In summary, the conversation discusses three questions related to vectors and their magnitudes. The first two questions are answered correctly, while the third one is solved incorrectly at first but eventually the correct answer of 200 is given. The method used to solve the third question is questioned and a different approach is suggested. The conversation also discusses the possible magnitudes that can be obtained by adding two vectors of magnitudes 200 and 40, with the conclusion that the only possible choice for the resulting magnitude is 200.
  • #1
wakejosh
102
0
I just wanted to make sure I'm doing my homework correctly, please let me know if any of the following is incorrect, if anyone knows. most the questions are multiple choice but I am just posting what I found to be the answer. thanks,:

1- What type of quantity is characterized by both magnitude and direction?

Vector

2- When we add a displacement vector to another displacement vector, the result is:

a displacement vector

3- A student adds two vectors. One has a magnitude of 200 and the other has a magnitude of 40. Which of the following is the only possible chice for the magnitude of the resultant?

ok, so I am assuming the vectors are at a right angle so I used the phthalgorym therom or whatever (A squared + B squared = C squared) and I came out with 204, and one of my choices was 200 (the other choices were 100,260, and 40) I am just a little scetchy on this answer and wondering if I should have gone about it a different way.


Any input is greatly appreciated. Thanks.
 
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  • #2
the first two are correct. you got the correct answer for the third one, but went about it incorrectly. Take a look at the answers given. With those two vectors could you add them in any way (doesn't have to be a right triangle) to make a vector of that length. For example, a vector of magnitude 260 could not be made from one of 200 and 40. For if they were added in the same direction it would only equal 240, the same type of logic applies to the other two incorrect ones. The answer of 200 could be made by a triangle (but not a right triangle) with two sides of length 200 and one of length 40.
 
  • #3
Regarding 3 - the only possible choice seems to be 200. You can draw a vector in any direction, and say it has a magnitude of 200. Then, you draw a circle of radius 40 with the centre on the 'top' of the vector whose magnitude is 200 (on the arrowhead :biggrin: ). Then it's obvious that the least vector has a magnitude 160, and the greatest 240. So, 100, 40, and 260 fall off.
 
  • #4
You got the first two ok. For the last one, I think you got the right answer, but why did you assume they are at right angles? The maximum possible magnitude is if both vectors are pointing in the same direction, in which case the magnitude would be 240, and the minimum is if they're going in opposite directions, giving 160. So you know the answer must be between 240 and 160.
 

FAQ: Little help with some simple Vector physics

1. What is a vector in physics?

A vector in physics is a quantity that has both magnitude (size or amount) and direction. It is represented by an arrow, where the length of the arrow represents the magnitude and the direction of the arrow represents the direction of the quantity.

2. How do you calculate the magnitude of a vector?

The magnitude of a vector can be calculated using the Pythagorean theorem, where the square of the magnitude is equal to the sum of the squares of its components. Alternatively, the magnitude can also be calculated using trigonometric functions when working with vectors in two or three dimensions.

3. What is the difference between a vector and a scalar quantity?

A scalar quantity only has magnitude, whereas a vector has both magnitude and direction. Examples of scalar quantities include mass, temperature, and time, while examples of vector quantities include displacement, velocity, and force.

4. How do you add or subtract vectors?

To add or subtract vectors, you can use the parallelogram rule or the head-to-tail method. For the parallelogram rule, you draw the two vectors with their tails at the same point, then complete the parallelogram with the two vectors as sides. The diagonal of the parallelogram represents the sum of the two vectors. For the head-to-tail method, you place the tail of the second vector at the head of the first vector, and the sum or difference of the two vectors can be drawn from the tail of the first vector to the head of the second vector.

5. How are vectors used in physics?

Vectors are used in physics to represent physical quantities that have both magnitude and direction. They are used to calculate forces, velocities, accelerations, and other important quantities in the study of motion and other physical phenomena. Vectors are also used to describe and analyze the behavior of particles and objects in various fields of physics, such as mechanics, electromagnetism, and thermodynamics.

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