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Two dogs pull horizontally on ropes attached to a post; the angle between the ropes is \(60.0^{\circ} .\) If \(\operatorname{dog} A\) exerts a force of 270 \(\mathrm{N}\) and dog \(B\) exerts a force of \(300 \mathrm{N},\) find the magnitude of the resultant force and the angle it makes with dog \(A\) 's rope.

Short Answer

Expert verified
Resultant force magnitude: 494.85 N, Angle with dog A's rope: 31.89°.

Step by step solution

01

Identify Forces and Angles

The forces exerted by the dogs are treated as vectors. Dog A exerts a force of \(F_A = 270 \, \mathrm{N}\) and dog B exerts a force of \(F_B = 300 \, \mathrm{N}\) at an angle of \(60.0^{\circ}\) between the ropes.
02

Calculate Components of Forces

We calculate the components of each force. Dog A's force is along the x-axis, so its components are \(F_{Ax} = 270 \, \mathrm{N}\) and \(F_{Ay} = 0\). Dog B's force has both x and y components, given by:\[ F_{Bx} = 300 \cos(60.0^{\circ}) = 150 \, \mathrm{N} \]\[ F_{By} = 300 \sin(60.0^{\circ}) = 259.81 \, \mathrm{N} \]
03

Find Resultant Force Components

Add the components of each force to find the resultant force: The x-component is:\[ F_{Rx} = F_{Ax} + F_{Bx} = 270 \, \mathrm{N} + 150 \, \mathrm{N} = 420 \, \mathrm{N} \]The y-component is:\[ F_{Ry} = F_{Ay} + F_{By} = 0 + 259.81 \, \mathrm{N} = 259.81 \, \mathrm{N} \]
04

Calculate Magnitude of Resultant Force

Use the Pythagorean theorem to calculate the magnitude of the resultant force:\[ F_R = \sqrt{F_{Rx}^2 + F_{Ry}^2} = \sqrt{420^2 + 259.81^2} \= \sqrt{176400 + 67500.2361} \= \sqrt{243900.2361} \\approx 494.85 \, \mathrm{N} \]
05

Find Angle with Dog A's Rope

Use the tangent function to find the angle of the resultant force with respect to dog A's rope:\[ \theta = \tan^{-1} \left(\frac{F_{Ry}}{F_{Rx}}\right) = \tan^{-1} \left(\frac{259.81}{420}\right) \\approx \tan^{-1}(0.6186) \\approx 31.89^{\circ} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Resultant Force
When multiple forces act at a point, they can be combined into a single equivalent force known as the resultant force. It represents both the direction and amount of total force applied. In the problem, the forces from both dogs need to be combined to find this resultant.
To compute the magnitude, we use trigonometry to find the individual x and y force components for each dog. These components are then added together to get the total or resultant force components in the x and y directions.When these components are known, we use the Pythagorean theorem to find the resultant force's magnitude:
  • Combine the x-components: \(F_{Rx} = F_{Ax} + F_{Bx}\)
  • Combine the y-components: \(F_{Ry} = F_{Ay} + F_{By}\)
  • Use: \(F_R = \sqrt{F_{Rx}^2 + F_{Ry}^2}\) to find the magnitude.
This step-by-step assembly ensures that you understand how individual forces contribute to the resultant, a crucial concept in physics.
Force Components
Decomposing force vectors into their components is a common technique in physics, especially when dealing with forces at angles. Each force can be thought of as contributing separately in two perpendicular directions: x (horizontal) and y (vertical).
  • Force along the x-axis: given directly or calculated by multiplying the force's magnitude by the cosine of its angle.
  • Force along the y-axis: calculated by the force's magnitude times the sine of the angle.
For example, in this scenario:- For Dog A, since the force is completely along the x-axis, \(F_{Ax} = 270\, \mathrm{N}\) and \(F_{Ay} = 0\).- For Dog B, with a 60-degree angle, the components are calculated as: \[F_{Bx} = 300 \cos(60^{\circ}) = 150\, \mathrm{N}\]\[F_{By} = 300 \sin(60^{\circ}) = 259.81\, \mathrm{N}\]Understanding how to break a force into components is crucial for solving many physics problems. It allows us to easily calculate how different forces interact based on direction.
Trigonometry
Trigonometry comes in handy when dealing with forces applied at angles. It helps us split forces into their components and find angles relevant to the situation.
Essential trig functions:
  • Cosine (\(\cos\)) - relates the adjacent side to the hypotenuse.
  • Sine (\(\sin\)) - relates the opposite side to the hypotenuse.
  • Tangent (\(\tan\)) - relates the opposite side to the adjacent side, often used to find angles.
In our problem, these functions are used to compute the x and y components of the forces exerted by the dogs. The inverse tangent function, \(\tan^{-1}\), is then utilized to find the angle of the resultant force with respect to the original force direction, offering insight into the force's overall direction.
Physics Problem Solving
Solving a physics problem systematically can make complex situations more manageable. Here are some general strategies:
  • Identify all forces and angles: Clearly define what forces are at play, their magnitudes, and the angles they form.
  • Break down steps: Divide the problem into smaller tasks, like finding the direction and magnitude of forces.
  • Use the right formulas: Apply known physics formulas to solve for unknown quantities, like resultant forces or angles.
  • Check your work: Ensure that each step logically follows the previous one and that calculations are correct.
In this exercise, the methodical approach of breaking down forces into components, finding their sum, and using trigonometry to identify the angle, illustrates effective problem-solving. These practices are essential, not just here but in tackling a wide variety of physics challenges.

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