Displacement and 1-D Kinematics

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SUMMARY

The discussion focuses on calculating the average velocity of a runner who covers 15 km in 20 minutes and then walks back to the starting point in 45 minutes. The average velocity is determined using the formula Vav = (Xf - Xi) / (tf - ti), where the total displacement is zero, leading to an average velocity of 0 km/h for the entire trip. Participants clarify the importance of breaking the problem into two parts: calculating the speeds for running and walking separately before averaging them.

PREREQUISITES
  • Understanding of kinematic equations, specifically Vav = (Xf - Xi) / (tf - ti)
  • Knowledge of speed calculation using S = d/t
  • Ability to convert time units from minutes to hours
  • Familiarity with the concepts of displacement and average velocity
NEXT STEPS
  • Study the implications of displacement in kinematics
  • Learn about the differences between speed and velocity
  • Explore more complex kinematic equations for multi-part motion
  • Practice problems involving average velocity in different scenarios
USEFUL FOR

Students studying physics, particularly those focusing on kinematics, as well as educators looking for examples of displacement and average velocity calculations.

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[SOLVED] Displacement and 1-D Kinematics

Homework Statement


A runner runs 15 km, in a straight line, in 20 min and then takes 45 min to walk back to the beginning. Find the average velocity for the whole trip.

Homework Equations


Vav= (Xf-Xi) / (tf-ti)


The Attempt at a Solution


Wouldn't the displacement be 0? If so; what is the average velocity of the whole trip? It couldn't be 0.

It would be 0. Silly me.
 
Last edited:
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Where is this equation from?

Tackle the problem from two parts: find the speed of his run, and the speed of his walk, and average them.

You know S = d/t yes? So convert the time to hours, do the question in two steps and average.
 


Yup; thanks. I figured it out.
 

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