Ruth sets out to visit her friend Ward, who lives 50 mi north and 100 mi east of her. She starts by driving east, but after 30 mi she comes to a detour that takes her 15 mi south before going east again. She then drives east for 8 mi and runs out of gas, so Ward flies there in his small plane to get her. What is Ward's displacement vector? Give your answer (a) in component form, using a coordinate system in which the y-axis points north, and (b) as a magnitude and direction.
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3. Vectors
Adding Vectors by Components
Problem 44
Textbook Question
A crate, seen from above, is pulled with three ropes that have the tensions shown in FIGURE P3.44. Tension is a vector directed along the rope, measured in newtons (abbreviated N). Suppose the three ropes are replaced with a single rope that has exactly the same effect on the crate. What is the tension in this rope? Write your answer in component form using unit vectors.


1
Step 1: Identify the forces acting on the crate. The three forces are T₁ = 20 N directed along the positive y-axis, T₂ = 32 N at an angle of 25° above the positive x-axis, and T₃ = 30 N at an angle of 45° below the negative x-axis.
Step 2: Resolve each tension vector into its x and y components using trigonometric functions. For T₂ and T₃, use the formulas: x-component = T * cos(θ) and y-component = T * sin(θ).
Step 3: Calculate the x and y components of each tension vector:
- T₁: x-component = 0, y-component = 20 N.
- T₂: x-component = 32 * cos(25°), y-component = 32 * sin(25°).
- T₃: x-component = -30 * cos(45°), y-component = -30 * sin(45°).
Step 4: Add the x-components of all three tensions to find the net x-component of the resultant tension vector. Similarly, add the y-components to find the net y-component of the resultant tension vector.
Step 5: Express the resultant tension vector in component form using unit vectors: T = (net x-component) î + (net y-component) ĵ.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vector Addition
Vector addition is the process of combining two or more vectors to determine a resultant vector. This involves adding the components of the vectors in each direction (x and y) separately. The resultant vector represents the cumulative effect of all the individual vectors acting together, which is crucial for solving problems involving forces, such as the tensions in the ropes.
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Components of a Vector
A vector can be broken down into its components along the coordinate axes, typically the x-axis and y-axis. Each component represents the influence of the vector in that direction. For example, a tension vector can be expressed as T = T_x i + T_y j, where T_x and T_y are the components along the x and y axes, respectively, and i and j are the unit vectors in those directions.
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Equilibrium of Forces
In physics, an object is in equilibrium when the net force acting on it is zero. This means that all the forces (or tensions, in this case) acting on the object must balance out. For the crate being pulled by the ropes, the sum of the x-components and the sum of the y-components of the tensions must equal zero, allowing us to find the equivalent single tension that would produce the same effect.
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