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Ch 03: Vectors and Coordinate Systems
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 3, Problem 30

Trevon drives with velocity v1 = (55î - 10ĵ) mph for 1.0 h, then v2 = (20î + 50ĵ) mph for 2.0 h. What is Trevon's displacement? Write your answer in component form using unit vectors.

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Step 1: Understand that displacement is the vector sum of the individual displacements during each segment of motion. Displacement for each segment can be calculated using the formula: d = vt, where v is the velocity vector and t is the time duration.
Step 2: Calculate the displacement for the first segment of motion. Use the velocity vector v1 = (55î − 10ĵ) mph and the time t = 1.0 h. Multiply the velocity vector by the time: d1 = (55î − 10ĵ) ⋅ 1.0.
Step 3: Calculate the displacement for the second segment of motion. Use the velocity vector v2 = (20î + 50ĵ) mph and the time t = 2.0 h. Multiply the velocity vector by the time: d2 = (20î + 50ĵ) ⋅ 2.0.
Step 4: Add the two displacement vectors to find the total displacement. Use the formula: dtotal = d1 + d2. Substitute the expressions for d1 and d2 from Steps 2 and 3.
Step 5: Write the total displacement in component form using unit vectors. Combine the î and ĵ components separately to express the result as dtotal = (xî + yĵ), where x and y are the combined components.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Velocity

Velocity is a vector quantity that describes the rate of change of an object's position with respect to time. It has both magnitude and direction, which means it can be represented in component form using unit vectors. In this question, Trevon's velocities v₁ and v₂ are given in terms of unit vectors, indicating how far he travels in the x (î) and y (ĵ) directions.
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Displacement

Displacement is the vector that represents the change in position of an object. It is calculated as the final position minus the initial position and is also expressed in component form. In this scenario, Trevon's total displacement will be the sum of the displacements from each segment of his journey, taking into account the time spent traveling at each velocity.
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Vector Addition

Vector addition is the process of combining two or more vectors to determine a resultant vector. This involves adding the corresponding components of the vectors. In this problem, Trevon's total displacement is found by calculating the displacement for each leg of his journey and then adding these vectors together to find the overall displacement in component form.
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Related Practice
Textbook Question

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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Textbook Question

A cannon tilted upward at 30° fires a cannonball with a speed of 100 m/s. What is the component of the cannonball's velocity parallel to the ground?

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Textbook Question

While vacationing in the mountains you do some hiking. In the morning, your displacement is Smorning=(2000m,east)+(3000m,north)+(200m,vertical)\(\mathbf{S}\)_{morning} = (2000 \, \(\text{m}\), \(\text{east}\)) + (3000 \, \(\text{m}\), \(\text{north}\)) + (200 \, \(\text{m}\), \(\text{vertical}\)). Continuing on after lunch, your displacement is Safternoon=(1500m,west)+(2000m,north)(300m,vertical)\(\mathbf{S}\)_{afternoon} = (1500 \, \(\text{m}\), \(\text{west}\)) + (2000 \, \(\text{m}\), \(\text{north}\)) - (300 \, \(\text{m}\), \(\text{vertical}\)). What is the magnitude of your net displacement for the day?

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Textbook Question

A cannonball leaves the barrel with velocity v = (75î + 45ĵ). At what angle is the barrel tilted above horizontal?

Textbook Question

The minute hand on a watch is 2.0 cm in length. What is the displacement vector of the tip of the minute hand in each case? Use a coordinate system in which the y-axis points toward the 12 on the watch face. From 8:00 to 9:00 a.m.

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Textbook Question

While vacationing in the mountains you do some hiking. In the morning, your displacement is Smorning=(2000m,east)+(3000m,north)+(200m,vertical)\(\mathbf{S}\)_{morning} = (2000 \, \(\text{m}\), \(\text{east}\)) + (3000 \, \(\text{m}\), \(\text{north}\)) + (200 \, \(\text{m}\), \(\text{vertical}\)). Continuing on after lunch, your displacement is Safternoon=(1500m,west)+(2000m,north)(300m,vertical)\(\mathbf{S}\)_{afternoon} = (1500 \, \(\text{m}\), \(\text{west}\)) + (2000 \, \(\text{m}\), \(\text{north}\)) - (300 \, \(\text{m}\), \(\text{vertical}\)). At the end of the hike, how much higher or lower are you compared to your starting point?

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