# What Is the Wind Velocity Affecting the Light Plane's Course?

• dfcitykid
In summary, the conversation discusses a problem where a light plane is initially headed due south with a speed of 185 km/h. After 1 hour, the pilot notices that they have covered only 135 km and their direction is now 75 degrees south of east. The question is to determine the wind velocity. The solution involves setting up a triangle and using the definition of relative velocity to find the velocity of the air relative to the ground. The conversation also provides a similar example to help understand the problem.
dfcitykid
A light plane is headed due south with a speed relative to still
air of 185 km/h. After 1 h, the pilot notices that they have
covered only 135 km and their direction is not south but 75˚ south
of east. What is the wind velocity?

I know I have to set up a triangle and solve from but there, but I don't even know how to draw it. Help please!

I just can't get the question. The plane had been moving due south with a relative speed of 185km/h. Then they decided to turn 75 degrees toward south of east, distancing 135 km in an hour. The question is to figure out what the wind velocity was. Is it the question?

@PaulDirac
The aircraft has an airspeed and bearing (given) but the plane has been blown by the wind so that the resulting motion over the ground is something else (also given). OP is being asked to find the direction and speed of the wind wrt the ground.

@dfcitykid
... you have to use the definition of the relative velocity.
You are given the velocities plane wrt ground and plane wrt air, and you want to find the velocity air wrt ground.
How are these velocities normally related to each other?

PaulDirac said:
I just can't get the question. The plane had been moving due south...

No. Its been heading/pointing south not moving south. Its movement over the ground has been affected by unexpected wind.

...I still don't get it :(

Where did we lose you?
Do you know how to add vectors?

A typical example would be:
Aircraft can fly at 60kmph wrt the air.
The wind is blowing at 30kmph due east.
The pilot wants to fly due south over the ground.
Which direction does he have to point the plane?

How would you normally do that problem?

## 1. What is relative velocity?

Relative velocity is the measurement of the velocity of an object in relation to another object. It takes into account the motion of both objects and their direction of movement.

## 2. How do you solve relative velocity problems?

To solve a relative velocity problem, you need to use the relative velocity formula, which is Vab = Va - Vb. This formula calculates the velocity of object A in relation to object B. Once you have the relative velocity, you can use it to solve for other variables in the problem, such as time or distance.

## 3. What are some common examples of relative velocity problems?

Examples of relative velocity problems include a boat crossing a river, a plane flying in the wind, or a car driving on a curved road. In each of these scenarios, the movement of one object is affected by the movement of another object.

## 4. Can relative velocity be negative?

Yes, relative velocity can be negative. This means that the two objects are moving in opposite directions. For example, if object A is moving at 10 m/s to the east and object B is moving at 5 m/s to the west, the relative velocity of object A in relation to object B would be -15 m/s.

## 5. How is relative velocity different from absolute velocity?

The main difference between relative velocity and absolute velocity is that relative velocity takes into account the motion of two objects, while absolute velocity only measures the motion of one object in relation to a fixed point. Absolute velocity is constant and does not change, while relative velocity can change depending on the movement of the two objects.

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