Constant Velocity (Finding when 2 objects will intersect)

  • Thread starter davyvfr
  • Start date
  • #1
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Homework Statement


"Jim leaves at noon and drives east on I-10 at 60mph, Jenny leaves from the same location at 1:30PM, but travels at 70mph. When and where will Jenny catch up to Jim?"


Homework Equations


None.


The Attempt at a Solution


When doing a similar problem in class, we used substitution/elimination to solve. Basically, I just can't seem to set it up into an equation for time and distance.
 

Answers and Replies

  • #2
gneill
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What formulas are you attempting to use to calculate their positions?
 
  • #3
Its a simple set of linear equations.

Figure out 2 equations,
1)The distance Jimmy is from the origin
2) The distance Jenny is from the origin.

Equate and you'll get your answer.
 
  • #4
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Hmm.

Ok, so would it be something like this?

y=70x+1:30
y=60x+12:00
 
Last edited:
  • #5
gneill
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2,854
Hmm.

Ok, so would it be something like this?

y=70x+1:30
y=60x+12:00
Define your variables. What does y represent? What does x represent? What are "1:30" and "12:00" supposed to mean in an equation? What units are attached to each of the quantities? Can you add "12:00" to "60x" and have it make sense?

Think of the clock times as representing moments when you might start or stop a separate stopwatch which can start at zero. That way you won't have to deal with the inconvenience of hours of the day that have no direct relevance to the problem.

In you classwork you must have been introduced to some formula that relates total distance to initial distance, velocity, and time traveled. What is it?
 

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