# Basic Kinematics Problem

1. May 7, 2014

### rr96

1. A plane is aimed north and is travelling 851 km/h. A wind blows the plane from 40° S of E at 36 km/h. What is the plane’s resultant velocity?

2. I think the answer is 828.3 km/h at 88.1° East of North but I am not sure.

Ay= 851

Bx= cosθ
cos40=x/36
x=27.6

By=sinθ
sin40=-y/36
y=-23.1

Rx=27.7

Ry=851-23.1
=827.9

a^2 + b^2 = c^2
(27.6)^2 + (827.9)^2 = c^2
c= 828.3

Using tan, θ=88.1

Last edited: May 7, 2014
2. May 7, 2014

### Greg Bernhardt

How did you reach your answer? We can then see where you might have gone wrong.

3. May 8, 2014

### SteamKing

Staff Emeritus
According to your answer, a plane originally traveling north is blown so far off course by a modest SEasterly wind that it winds up traveling almost due east. Who needs hurricanes?

If the wind is coming from the SE and the plane is traveling north, is the plane experiencing a headwind or a tailwind?

In these problems, drawing a simple sketch helps to clarify the direction of the various vector components.

4. May 8, 2014

### haruspex

We cannot see inside your head. When you make up symbols for variables, unless the meanings are blindingly obvious, please state what they represent.

5. May 8, 2014

### ciubba

The numbers look good, but I do not believe that you have interpreted the location of theta properly. Are you certain that theta is made between the y-axis and the Resultant vector i.e. east of north?