Math Problem Statement

A stubborn dog is being walked on a leash by its owner. At one point, the dog encounters an interesting scent at some spot on the ground and wants to explore it in detail, but the owner gets impatient and pulls on the leash with force F = (94.0 i + 133 j + 34.0 k) N along the leash.

Part 1

What is the magnitude of the pulling force?

Part 2

What angle does the leash make with the vertical?

Solution

Part 1: Finding the Magnitude of the Pulling Force

The pulling force is given as F=(94.0i^+133j^+34.0k^)N\mathbf{F} = (94.0 \, \hat{i} + 133 \, \hat{j} + 34.0 \, \hat{k}) \, \text{N}. To calculate the magnitude of the force, we use the formula for the magnitude of a vector:

F=Fx2+Fy2+Fz2|\mathbf{F}| = \sqrt{F_x^2 + F_y^2 + F_z^2}

where Fx=94.0F_x = 94.0, Fy=133F_y = 133, and Fz=34.0F_z = 34.0. Let's calculate the magnitude:

F=(94.0)2+(133)2+(34.0)2|\mathbf{F}| = \sqrt{(94.0)^2 + (133)^2 + (34.0)^2}

F=8836+17689+1156|\mathbf{F}| = \sqrt{8836 + 17689 + 1156}

F=27681|\mathbf{F}| = \sqrt{27681}

F166.35N|\mathbf{F}| \approx 166.35 \, \text{N}

So, the magnitude of the pulling force is approximately 166.35 N.


Part 2: Finding the Angle with the Vertical

The vertical direction is along the k^\hat{k} axis, so we want to find the angle θ\theta that the leash makes with the vertical. The angle between two vectors is given by:

cosθ=FkFk\cos \theta = \frac{\mathbf{F} \cdot \mathbf{k}}{|\mathbf{F}| \cdot |\mathbf{k}|}

Here, k=(0,0,1)\mathbf{k} = (0, 0, 1) and F=(94.0,133,34.0)\mathbf{F} = (94.0, 133, 34.0). The dot product Fk\mathbf{F} \cdot \mathbf{k} is simply the zz-component of F\mathbf{F}, which is 34.0.

Thus,

cosθ=34.0F\cos \theta = \frac{34.0}{|\mathbf{F}|}

Substitute the magnitude of F|\mathbf{F}| from Part 1:

cosθ=34.0166.35\cos \theta = \frac{34.0}{166.35}

cosθ0.2044\cos \theta \approx 0.2044

Now, take the inverse cosine to find the angle:

θ=cos1(0.2044)78.2\theta = \cos^{-1}(0.2044) \approx 78.2^\circ

So, the angle that the leash makes with the vertical is approximately 78.2 degrees.


Let me know if you'd like further details or have any questions. Here are 5 related questions to consider:

  1. How would the magnitude of force change if each component doubled?
  2. What if the leash were pulled horizontally, how would that affect the angle?
  3. What happens to the pulling force's magnitude if the vertical component kk is zero?
  4. How can we find the angle with the horizontal instead of the vertical?
  5. What if frictional force acted against the pulling force?

Tip: When working with vectors, always remember that the dot product helps to find the projection of one vector in the direction of another.

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Math Problem Analysis

Mathematical Concepts

Vector Magnitude
Dot Product
Trigonometry

Formulas

Magnitude of a vector: |F| = sqrt(Fx^2 + Fy^2 + Fz^2)
Angle with vertical: cos(θ) = Fz / |F|

Theorems

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Suitable Grade Level

Grades 11-12