Hi Guys Can You Help Me With Vectors

Maths, vectors? Exam tomorrow?

Relative to an origin O, the position vectors of the points A and B are given by
→
OA = 2i − 8j + 4k

and

→
OB = 7i + 2j − k.

(i) Find the value of:
→ →
OA.OB and hence state whether angle AOB is acute, obtuse or a right angle.

(ii) The point X is such that:
→ →
AX = 2/5AB.

Find the unit vector in the direction of OX.


Please tell me how you got each answer? I know the first part but I don't know if it's obtuse or right angle? How do I know it's obtuse or right angle??

Hi guys please help me i have exam phisics tomorrow .please help help!!!!!!!!!!!!!!!!!!!!!!!!?

The acceleration vector is (αt^2, β-γt )

Integrate with respect to time to get the velocity vector: (αt^3 /3 + A, βt-γt^2/2 + B)

Find the constants A and B by plugging in initial conditions for velecity

Then integrate again to get the position vector....

Simple vector calculus help, simple but confusing?

The component of a vector E along another vector F is the orthogonal projection of E onto a straight line parallel to F

The component of E in the direction of F is:
|E| cos(alpha) where alpha is the angle between E and F.

The dot product E∙F is defined as:
E∙F= |E| |F| cos(alpha)

The component of E along F is therefore:
E∙F / |F|

E = (0,3,4)
F = (4,10,5)

E∙F = 0∙4 + 3∙10 + 4∙5 = 50
|F| = √(4^2 + 10^2 + 5^2) = √141

The component of E along F is:
|E| cos(alpha) = E∙F / |F| = 50/√141

Need help with vectors, c++?

To place the value 4 into third row, second column, use grid[2][1] = 4; (rows and columns are counted from zero)

for example:

#include
#include
int main()
{
     // 9x9 vector of vectors
     std::vector< std::vector > grid(9, std::vector(9));

     // put the number 4 in 3rd row 2nd column
     grid[2][1] = 4;

     // output
     for(size_t r=0; r     {
         for(size_t c=0; c             std::cout << grid[r][c] << ' ';
         std::cout << '\n';
     }
}

test: https://ideone.com/sCN0T

Vector math question involving u, v and w.?

note the following vectors:

X = v - u, the vector from endpoint of u to endpoint of v
Y = w - v, the vector from endpoint of v to endpoint of w

we have:
X x Y = (v-u) x (w-v)
= v x w - u x w + u x v
= v x w + w x u + u x v
= 0 according to the assumption.

So X and Y are collinear, which also means the endpoints are on a same line.

It could also mean X=0 or Y=0, but in these cases, two of the original vectors are equal, in which case the endpoints of these three vectors are trivially on a same line.

Electromagnetics question ,plsss help me guys?

given two vectors rA= -ax-3ay-4az and rB=2ax+2ay+2az

find rab

and the answer is

RAB =(2+1)ax +(2+3)ay +(2+4)az
RAB= 3ax+5ay+6az

now my question is about the signs..why the two vectors added with positive sign..isnt it that it should rab=(2-1)ax+ (2-3)ay+(2-4)az

pls help me how to add vectors..wheter from positive to negative..please explain it to me guysss.plsss

Electric field problem (physics)?

hey guys can you help me with this one??

Consider an electric field of E=(a,b,c) (a,b,c are constants). What is the work required to move an electron a distance 'd' in the negative x direction?

I have tried doing it and have no clue how to!!!!!