Math Problem Statement

A swimmer starts swimming north at a velocity of 5 m/s while the current is taking her at 8 m/s at an angle of 300 degrees. How far is she from the start after 5 minutes?

Solution

To solve this problem, we need to determine the swimmer's total displacement after 5 minutes by considering both her own velocity and the velocity of the current.

Step 1: Decompose the current's velocity

The current is moving at 8 m/s at an angle of 300°. To break this down into its horizontal (xx) and vertical (yy) components, we use trigonometry:

  • Vx=8cos(300)V_{x} = 8 \cos(300^\circ)
  • Vy=8sin(300)V_{y} = 8 \sin(300^\circ)

Since cos(300)=12\cos(300^\circ) = \frac{1}{2} and sin(300)=32\sin(300^\circ) = -\frac{\sqrt{3}}{2}, we get:

  • Vx=8×12=4m/sV_{x} = 8 \times \frac{1}{2} = 4 \, \text{m/s}
  • Vy=8×32=436.93m/sV_{y} = 8 \times -\frac{\sqrt{3}}{2} = -4\sqrt{3} \approx -6.93 \, \text{m/s}

Step 2: Combine the swimmer's velocity and the current's velocity

The swimmer is moving north (in the positive yy-direction) at 5 m/s, so her total velocity in the yy-direction is the sum of her velocity and the yy-component of the current:

  • Vy,total=5+(6.93)=1.93m/sV_{y, \text{total}} = 5 + (-6.93) = -1.93 \, \text{m/s}

In the xx-direction, only the current is contributing to the velocity:

  • Vx,total=4m/sV_{x, \text{total}} = 4 \, \text{m/s}

Step 3: Find the total displacement after 5 minutes

The swimmer is moving for 5 minutes, which is 300 seconds. Now, we calculate her displacement in the xx and yy directions:

  • Dx=Vx,total×t=4×300=1200mD_{x} = V_{x, \text{total}} \times t = 4 \times 300 = 1200 \, \text{m}
  • Dy=Vy,total×t=1.93×300=579mD_{y} = V_{y, \text{total}} \times t = -1.93 \times 300 = -579 \, \text{m}

Step 4: Calculate the total displacement

The total displacement is the magnitude of the resultant vector:

Dtotal=Dx2+Dy2=12002+(579)2=1440000+335241=17752411332.26mD_{\text{total}} = \sqrt{D_{x}^2 + D_{y}^2} = \sqrt{1200^2 + (-579)^2} = \sqrt{1440000 + 335241} = \sqrt{1775241} \approx 1332.26 \, \text{m}

Thus, the swimmer is approximately 1332.26 meters from her starting point after 5 minutes.


Would you like further details or have any questions?

Here are 5 related questions:

  1. How would the problem change if the current's velocity was 10 m/s?
  2. What if the swimmer were swimming south instead of north?
  3. How would you calculate the time taken to reach a certain distance?
  4. How would the calculation change if the current's direction was 45 degrees?
  5. How does the angle of the current affect the displacement?

Tip: Always break down vectors into components when dealing with motion at angles.

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Math Problem Analysis

Mathematical Concepts

Vector Decomposition
Trigonometry
Pythagorean Theorem

Formulas

V_x = V * cos(θ)
V_y = V * sin(θ)
Displacement = Velocity * Time
Total Displacement = √(D_x^2 + D_y^2)

Theorems

Pythagorean Theorem
Trigonometric Decomposition

Suitable Grade Level

Grades 10-12