# 1D Kinematics - Integration of the Equations of Motion

1. Jan 17, 2013

### bearjew11

1. The distance from two airports is 1286 km by air. Plane A leaves the first airport at 10:00a heading north toward the second airport, another plane leaves from the second airport at 11:00a heading south towards the destination plane A originally departed from. Plane A travels at 720km/h, and plane B, slowed by a headwind, travels at 640km/h. Where do the planes meet? At what time?

Given:
Δy= 1286km
Vp1 = 720km/h
Vp2 = 640km/h
Δt = ?
??

2. Not quite sure yet.

3. I tried to draw a graph but it, unfortunately, got me no where.

2. Jan 17, 2013

### Staff: Mentor

If t is the clock time, how far north has the first plane traveled by time t?
How far south has the second plane traveled by time t?

When the two planes meet, how are their distances from their respective starting points related to the total distance 1286 km?

3. Jan 18, 2013

### bearjew11

Well, if plane A left an hour before plane B, then the distance is no longer 1286km, (assuming that the position of plane A is 0). The two planes have to, instead, cover 566km to meet, 1286 - 720* 1 = 566km

After 1 hour, or 3600s, plane A has traveled north 720,000m and plane B is beginning to cover distance.

My attempt at a solution:
Knowns and unknowns:
For plane A:
VA = 720km/h = 200m/s - velocity
xA = 0km - position
VB = 640km/h ~~ 178m/s
xB = 1268km - (720km*1h) = 566km = 566000m
xm = ? - position where planes meet

Equations used:
t = xB/[VA + VB] = 566000/(200+178) ~~ 1,497.35s - when they meet
xm = VA*(t) = 200*(1497.35) = 299,470m - where they meet

4. Jan 18, 2013

### Staff: Mentor

Nice job.

I think they were asking for the clock time that they meet. 1495.35 sec ~ 25 minutes, so they meet at ~11:25.

Chet