#### Transcript 4-2 Components of Vectors

### 4-2 Components of Vectors

### Choosing a Coordinate System

No correct answer on how to choose Choosing a Correct coordinate system will better allow certain problems to be solved ◦ ◦ Similar to laying a grid down on a sheet of paper ◦ Choose the center of the grid (origin) On Earth: generally us the four Directions Through air: *x-axis *chosen to be horizontal and *y-axis* chosen to be vertical Direction of a vector is defined as the angle made with the *x-axis *measured counterclockwise

### Components

◦ ◦ A vector may be broken up into two component vectors.

◦ Parallel with *x-axis *(**A**

*x )*

◦ Parallel with y-axis *( A*

*y )*

Original Vector * A *is the sum of the two component vectors

*=*

**A**

**A***x + A y*

**Vector Resolution **is the process of breaking a vector into it’s components

### Components

All algebraic calculations involve only the components of vectors, not the vector itself ◦ Find by using Trigonometry ◦ ◦ Components are calculated where angle θ is measured counterclockwise from positive *x-axis*

*A x A y = A cos θ ; cos = A sin θ ; sin θ θ = (adjacent side/hypotenuse) = A x = (opposite side/hypotenuse) = A y / A / A*

### Practice

A bus travels 23.0 km on a straight road that is 30 o E. Where are the east and north components of its displacement?

N of Sketch problem Known: *A = 23.0 km* Unknown: *Ax = ?* ◦ ◦

**Calculation**

◦ *Ax = A *cos θ ; ◦ *= +*19.0 km *Ay = A *sin

*θ*

*= +*11.5 km

*; = 30 Ay = ?*

*o Ax = (23.0 km)cos 30 Ay = (23.0 km)sin 30 o o*

### Practice

What are the components of a vector of a magnitude 1.5 m at an angle of 35 o form the positive *x-axis*?

### Algebraic Addition of Vectors

◦ ◦ Two or more vectors (* A, B, C,…*) may be added by first resolving each vector to its

*x & y*components ◦ The

*x-components*are added to form the resultant (Rx) ◦ ◦

*R x = A x + B x + C x + …*

The *y-components *are added to form the resultant (Ry) ◦

*R y = A y + B y + C y + …*

To find the angle or direction of the resultant, the tangent of the angle that the vector makes with the *x-* *axis *is the following (*tan *

*θ = R y /R x )*

Find the angle by using the tan -1 key

### Algebraic Addition of Vectors

Cy B y A y A x A C B B x C x

*R x R R y*

### Practice

A GPS reciever told you that your home was 15.0 km at a direction 40 o North of West, but the only path led directly north. If you took that path and walked 10.0 km, how far, and in what direction would you have to walk to reach your home?

Draw the resultant vector, * R *from your original location to home Draw

*, the known displacement Draw*

**A***, the unknown displacement*

**B** A GPS reciever told you that your home was 15.0 km at a direction 40 o North of West, but the only path led directly north. If you took that path and walked 10.0 km, how far, and in what direction would you have to walk to reach your home?

R x = R cos θ ; (15.0 km) cos R y = R sin θ A x ; (15.0 km) cos = 0.0 km; A y = 10.0 km

*R = A + B; so B = R – A *

θ θ 140 140 o ; o ; = -11.5 km = +9.6 km B B x y = R x = R y B = √ B x – A x – A y = (-11.5 km) – (0.0 km) = -**11.5 km** = (9.6 km) – (10.0 km) = **-0.4 km** 2 = 11.5 km + B y 2 = √ (-11.5 km) 2 + (-0.4 km) 2 tan θ θ = B y /B x = (-0.4 km)/(-11.5 km) = +0.035

= tan-1(+0.035) = 2.0

o * B *= 11.5 km, 2.0

o south of west