Typical when do they collide problem

  • Thread starter Ohoneo
  • Start date
  • #1
Typical "when do they collide" problem

Homework Statement

In a historical movie, two knights on horseback start from rest 92 m apart and ride directly toward each other to do battle. Sir George's acceleration has a magnitude of 0.18 m/s2, while Sir Alfred's has a magnitude of 0.34 m/s2. Relative to Sir George's starting point, where do the knights collide?

Homework Equations

I would guess the 4 kinematics equations (as acceleration is constant)
v = v0 + at
x = 1/2(v0+v)t
x = v0t + 1/2 at^2
v^2 = v0^2 + 2ax

The Attempt at a Solution

Well, basically I think my attempts ended up being long and fruitless. I had NO idea how to start this problem and tried finding the position by hand plugging in 1, 2, 3, etc for time and figuring out how close the knights were coming to each other. Didn't work so well.
I thought I should make two equations equal to each other but didn't know what equations or where to start. Now I think I should be replacing t or x (position) in one of the equations, since I'm missing two variables instead of just one but I'm not sure how to relate the two... Any help at all is appreciated!
  • #2

Both knights travel with constant acceleration and start form zero velocity. So what are the distances (s1 and s2) traveled by both knights in time t?
Initially, the knights are 92 m apart. As they ride toward each other, the distance between them gradually decreases. Write up the distance between the knights as terms of t.

  • #3

Thank you so much :) I solved the problem. I had to basically eliminate t from the problem, as I was looking for x (relative to George). Thanks again!

Suggested for: Typical when do they collide problem