Understanding Relative Velocity of Runners Moving in Opposite Directions

Click For Summary
SUMMARY

The discussion focuses on the concept of relative velocity in physics, specifically regarding two runners, James and Billy, who are moving in opposite directions. James runs west at a certain speed, while Billy runs east at twice that speed. The relative velocity of James with respect to Billy is analyzed in two scenarios: when they run toward each other and when they run away from each other. The key takeaway is that the relative velocity is calculated using the equation Vb = -2Vj, where the negative sign indicates the opposite directions of their velocities.

PREREQUISITES
  • Understanding of basic physics concepts, particularly relative velocity
  • Familiarity with vector notation and directionality in motion
  • Knowledge of how to apply equations of motion in one dimension
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the principles of relative velocity in physics
  • Learn how to represent velocities using vector notation
  • Explore one-dimensional motion equations and their applications
  • Practice solving relative motion problems with varying speeds and directions
USEFUL FOR

This discussion is beneficial for high school physics students, educators teaching motion concepts, and anyone looking to deepen their understanding of relative velocity in kinematics.

samisoccer9
Messages
11
Reaction score
0

Homework Statement


James is running west wrt the ground and Billy is running east wrt the ground, but twice as fast as James. How does the relative velocity of James wrt Billy differ if they are running toward each other or away from each other? Explain.
*wrt = with relation to*

Homework Equations


VJG and VBG

The Attempt at a Solution


This is a word problem, I just started an online grade 12 physics class today so I am sort of clueless and quite confused. So I interpreted it like this. Let's say James was 100m/s, therefore Billy is 200m/s. If they run away from each other, so one left/west one right/east then in relation to the ground it would seem as if Billy covered more distance (which would be true?) and if they were running towards each other, then I thought it would be seen as Billy simply again covering more distance by the time James got there. I need help, please and thanks!
 
Physics news on Phys.org
Drawing a picture will help with almost every physics problem.

Rather than assign a number to the velocities, it is better to use symbols, like Vb and Vj for the velocities of james and billy relative to the ground.

Then Vb = -2Vj

Think about why the sign is negative.
 

Similar threads

Ray optics: velocity of image reflected off a moving mirror
  • · Replies 5 ·
Replies
5
Views
2K
Relative velocity passing a ball between two soccer players
  • · Replies 5 ·
Replies
5
Views
3K
Calculate the relative angular velocity
  • · Replies 2 ·
Replies
2
Views
2K
Runner's Average Velocity: 0.014 m/s
  • · Replies 17 ·
Replies
17
Views
2K
Problem using vectors and relative motion
  • · Replies 12 ·
Replies
12
Views
4K
Trying to understand the logic behind adding vectors with an angle between them
  • · Replies 14 ·
Replies
14
Views
2K
Relative Velocity Airplane Problem
  • · Replies 14 ·
Replies
14
Views
7K
High School Prove the velocity of a moving object is absolute in one IRF?
  • · Replies 22 ·
Replies
22
Views
2K
Relative Velocity and Angles of Movement (Sears & Zemansky's Exercise)
  • · Replies 11 ·
Replies
11
Views
3K
How Fast Does Spaceship A Move Relative to Spaceship B?
  • · Replies 19 ·
Replies
19
Views
3K