# Homework Help: Jet Planes

1. Sep 8, 2010

### Allura

1. The problem statement, all variables and given/known data

A jet plane is cruising at 300 m/s when suddenly the pilot turns the engines up to full throttle. After traveling 2 km, the jet is moving with a speed of 400 m/s. What is the jet's acceleration (in m/s/s) during this interval assuming the acceleration to be constant?

2. Relevant equations

I was thinking that in order to go further you would have to solve for the seconds? So I used v=m/s and solved for s, which was then 5s. But I'm not sure where to go from there?

Help?

2. Sep 8, 2010

### rl.bhat

Initial and final velocities are given. Displacement is given. Find the kinematic equation which relates Vi, Vf, x and a. And solve for a.

3. Sep 9, 2010

### Allura

But the only kinematic formulas I find include time, which isn't given.

4. Sep 9, 2010

### Allura

Well, I tried vf=vi+a(t) but I got 20m/s/s, which was wrong.

5. Sep 9, 2010

### rl.bhat

v2f - v2i = 2as

Substitute the values and find a. Here s = 2000 m.