Posted by **Lindsay** on Wednesday, October 3, 2007 at 1:25pm.

A Cessna airplane can accelerate from rest to a ground speed of 78 knots in 29.8 s. What is the average acceleration of this airplane?

I figured out that 78 knots is equal to 89.76 miles, 144.45 km, or 144,450 m. And I think the equation might be average=delta V over delta t. But I'm not sure if this is right...help!

- Physics -
**Quidditch**, Wednesday, October 3, 2007 at 2:48pm
You are thinking correctly. Delta v over delta t expresses acceleration.

delta v = 78kts (nautical miles/second) (convert to other units if desired.

delta t = 29.8s

average acceleration = (78/29.8) nautical miles/sec^2.

- Physics -
**Lindsay**, Wednesday, October 3, 2007 at 3:23pm
I try this and I get 2.62 knots/s^2, but it says this answer is wrong. Is it?

- Physics -
**Lindsay**, Wednesday, October 3, 2007 at 3:28pm
N/m, I needed to convert to knots to meters per second. I got the right answer.

Thanks for the help, Quidditch. :)

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