# Homework Help: The least constant acceleration

1. Sep 6, 2006

### physics newb

OK, heres the problem:
A large plane needs to get to a speed of 360 km/h on it's runway in order to take off. The runway is 1.8 km long. What would be the least constant acceleration required to take off?

Physics just started, I need shock paddles to get me going again :surprised

Thanks

2. Sep 6, 2006

### Päällikkö

Please show your own work. You must at least have some idea as to what equations to use?

3. Sep 6, 2006

### physics newb

Would it have to have a constant acceleration of 200 km/h to reach it's top speed by the end of the runway, or am I missing something?

Last edited: Sep 7, 2006
4. Sep 7, 2006

### physics newb

Well, I divided 360 km/h by the distance, 1.8 km, and got 200. Is that the least constant acceleration needed to take off? I'm very confused.

5. Sep 7, 2006

### Kurdt

Staff Emeritus
6. Sep 7, 2006

### physics newb

So I think the next thing I need to do is figure out the time it takes to reach that speed along that distance. So what was this 200 I was getting? 200 km/h?

I have the speed, I have the distance, how do I find the time it took to do this, or am I going off course?

7. Sep 7, 2006

### Kurdt

Staff Emeritus
try

$$v^2 = u^2 +2as$$

and rearrange for acceleration, a.