Vector Question: Swimmer Across River Diagram Help

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In summary, a swimmer is crossing a river that is flowing at 7km/h. The swimmer's speed relative to the water is 8km/h. The width of the river is 362m. To calculate the swimmer's speed directly across the river, a triangle of velocities can be drawn using the river's flow and the swimmer's speed. Once the speed is determined, it is easy to solve for other questions.
  • #1
Apollonian
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Homework Statement


A swimmer heads across a river flowing at 7km/h.
Her speed relative to the water is 8km/h.
The river is 362m wide.
There are other questions; however, I just need help with the diagram.

Homework Equations





The Attempt at a Solution


I'm not too sure on how to draw the diagram- I made a right angle triangle with the bank as shown in the picture. Is this correct?
 

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  • #2
Not quite.

The river is flowing (right) at 7km/hr
The swimmer moves (diagonally) at 8km/hr

So you can calculate how fast the swimmer is moving directly across the river by drawing a triangle of velocities.

Once you've got the speed it's easy.
 
  • #3
Oh I see what you mean, i wasn't sure if relative to implied it was the true course. Thank you.
 

1. How do I calculate the magnitude of the vector in this diagram?

To calculate the magnitude of a vector, you can use the Pythagorean theorem, which states that the magnitude is equal to the square root of the sum of the squares of the vector's components. In this diagram, the components of the vector would be the length and width of the river. Once you have the components, you can plug them into the formula to find the magnitude.

2. What is the direction of the vector in this diagram?

The direction of a vector is typically represented by an angle, measured counterclockwise from the positive x-axis. In this diagram, the direction of the vector would be the angle between the river and the swimmer's path. You can use trigonometric functions, such as tangent or sine, to determine this angle.

3. How do I find the resultant vector in this diagram?

The resultant vector is the vector that represents the combined effect of multiple vectors. In this diagram, the swimmer's motion can be broken down into two vectors: one along the river's current and one perpendicular to it. To find the resultant vector, you can use the parallelogram rule or the head-to-tail method to add these two vectors together.

4. What does the negative sign in front of the vector mean?

The negative sign in front of a vector indicates its direction. In this diagram, a negative sign would mean that the vector is pointing in the opposite direction of the positive x-axis. This could represent the swimmer's motion against the current of the river.

5. How does the length of the vector impact the swimmer's motion?

The length of a vector, or its magnitude, represents the strength or intensity of the vector's effect. In this diagram, a longer vector would mean a stronger current or a greater distance the swimmer would have to travel. A shorter vector would indicate a weaker current or a shorter distance to cross.

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