Math Problem Statement

Solve

A bus makes a trip according to the position-time graph shown. What is the average velocity (magnitude and direction) of the bus during segment A, segment B, and segment C? Express your answers in km/h.

Solution

Let's analyze the problem based on the image provided. The graph is a position-time graph, and we are asked to find the average velocity (in km/h) during the three segments A, B, and C of the bus's journey.

Steps to solve:

The average velocity vavgv_{\text{avg}} for each segment is calculated as:

vavg=ΔxΔtv_{\text{avg}} = \frac{\Delta x}{\Delta t}

Where:

  • Δx\Delta x is the change in position (displacement),
  • Δt\Delta t is the change in time.

Now, let's break down each segment:

Segment A (0 to 1 hour):

  • Initial position: xi=40kmx_i = 40 \, \text{km}
  • Final position: xf=0kmx_f = 0 \, \text{km}
  • Time interval: t=1.0hourt = 1.0 \, \text{hour}

vavg(A)=xfxit=0401.0=40km/hv_{\text{avg}}(A) = \frac{x_f - x_i}{t} = \frac{0 - 40}{1.0} = -40 \, \text{km/h} However, the user entered 16.67km/h-16.67 \, \text{km/h}, which seems incorrect, as the correct velocity should be 40km/h-40 \, \text{km/h}.

Segment B (1 to 2 hours):

  • Initial position: xi=0kmx_i = 0 \, \text{km}
  • Final position: xf=20kmx_f = -20 \, \text{km}
  • Time interval: t=1.0hourt = 1.0 \, \text{hour}

vavg(B)=xfxit=2001.0=20km/hv_{\text{avg}}(B) = \frac{x_f - x_i}{t} = \frac{-20 - 0}{1.0} = -20 \, \text{km/h} The user entered 10km/h10 \, \text{km/h}, which is also incorrect; the correct value should be 20km/h-20 \, \text{km/h}.

Segment C (2 to 3 hours):

  • Initial position: xi=20kmx_i = -20 \, \text{km}
  • Final position: xf=40kmx_f = 40 \, \text{km}
  • Time interval: t=1.0hourt = 1.0 \, \text{hour}

vavg(C)=xfxit=40(20)1.0=601=60km/hv_{\text{avg}}(C) = \frac{x_f - x_i}{t} = \frac{40 - (-20)}{1.0} = \frac{60}{1} = 60 \, \text{km/h} The user entered 40km/h40 \, \text{km/h}, but the correct velocity should be 60km/h60 \, \text{km/h}.

Summary of Correct Answers:

  • (a) vavg(A)=40km/hv_{\text{avg}}(A) = -40 \, \text{km/h}
  • (b) vavg(B)=20km/hv_{\text{avg}}(B) = -20 \, \text{km/h}
  • (c) vavg(C)=60km/hv_{\text{avg}}(C) = 60 \, \text{km/h}

Would you like further details on any step, or have any questions?


Here are 5 related questions you could explore:

  1. How do you determine displacement from a position-time graph?
  2. What is the difference between average velocity and average speed?
  3. How do you calculate velocity if the graph is non-linear?
  4. How can you interpret positive vs negative velocities on a graph?
  5. How is instantaneous velocity different from average velocity?

Tip: Always keep in mind that velocity is a vector quantity, meaning it has both magnitude and direction.

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Math Problem Analysis

Mathematical Concepts

Kinematics
Velocity
Position-Time Graphs

Formulas

Average velocity: v_avg = (Δx) / (Δt)

Theorems

Kinematic Equations of Motion

Suitable Grade Level

Grade 10-12