# Homework Help: Airplane question

1. Oct 9, 2005

### Izekid

I have a hard one here :
The lane for starting a airplane must be long enough for a airplane to accelerate to 300km/h with a constant acceleration on 1.6m/s2. How long must the startlane be?

This is what I've found out,

I take 300km/h and make it to m/s
300 / 3.6 = 83,3m/s
Then I because I don't know the time I take
t=v/a 83,3/1,6=132,8sek
Then I take
S=1/2(v0+v)*t = 1/2(0+83)*132,8 = 5511m = 5,5km

But I think that's not the right answer what have I done wrong?

Thankful for all help

2. Oct 9, 2005

### FredGarvin

There is a solution to this problem. Basic constant acceleration equations are your best friend here.

You were right to convert your final velocity to m/s. You also have an initial velocity which is not stated, but you can say that initial velocity is 0.

You made a mistake with your time calculation. (83.3)/(1.6) can not be 132 sec. You are dividing by a number bigger than 1. The number must be smaller than 83.3. There's the hint for you. Your last step was correct but using the wrong time number.

3. Oct 10, 2005

### Izekid

thx... small stupid misstakes