# What is the scalar product V_1(DOT)V_2 ?

Rellsun

## Homework Statement

Vector V_1 points along the z axis and has magnitude V_1 = 80. Vector V_2 lies in the xz plane, has magnitude V_2 = 51, and makes a -49o angle with the x axis (points below x axis)

## Homework Equations

A.B=ABCos(theta)=AxBx+AyBy+AzBz

Cos(theta)=(AxBx+AyBy+AzBz)/AB

## The Attempt at a Solution

im not really sure where to go from here im not sure if those equations are useful

Homework Helper
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The equations are indeed useful. Find the x,y and z components of each vector, then apply the first equation that you posted.

Rellsun
ok that helps a lot i dont know why i did do that. but how do you find the z component of the V_2=51?

Last edited:
Homework Helper
Gold Member
2021 Award
Vector V_2 lies in the xz plane, has magnitude V_2 = 51, and makes a -49o angle with the x axis (points below x axis)

Draw yourself two axes in the plane of the paper. Label the horizontal one x and the vertical one z (instead of the usual y). Draw the vector as indicated. Can you find its x and z components?

Rellsun
ahh thanks that makes much more sense. i got the final answer to be -3079.2 which is indeed correct. the help is appreciated.