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#### shyvr6

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Not sure what I'm missing, but my brain is fried over these basic questions.

1. A 1100·kg elevator is attached to a cable whose tension is 11200·N. What is the magnitude of the elevator's acceleration?

2. A fighter pilot flying with a speed of 500·m/s makes a turn with a radius of 5250·m. What centripetal acceleration does the pilot experience?

Thanks for any help.

#### silenced

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I did physics last year in school, so I'm gonna give this a shot.

1. The difference between the gravitational force on the elevator and the tension in the cable is what forces the elevator to go up or down.

Gravitational force = mg = 1100 kg (9.8 m/s^2) = 10780 N
Tension > 10780 N therefore the elevator is going up.
Tension - Gravitational force = 11200 N - 10780 N = 420 N
This force is what accelerates the elevator upward.

Acceleration of the elevator = Force/Mass = 420 N/ 1100 kg = 0.38 m/s^2

2. The equation for centripetal acceleration is

a = v^2/r velocity squared divided by radius

so it would be ((500 m/s)^2)/5250 m = 47.6 m/s^2

I hope these answers are correct, someone else please correct me if I'm wrong. shyrv6 I hope this helped you!

#### mind_games

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Just when you give the final answer for the 2nd question I think its best to mention the direction of the acceleration as well, even though its obvious. Because (and I had to look this up) acceleration is a vector it has magnitude and direction. Some teachers can get anal if you don't mention the direciton.
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So the pilot's acceleration is toward the center of that radius or 'toward the instantaneous center of curvature of the path' according to wiki.

[Edit: The first question asks for magnitude so direction is not important.]

#### shyvr6

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Thanks guys! For the second one, that's the answer I got, but it said I got it wrong. I forgot to add that it said to express it in g's (multiples of 10·m/s2), so how would I write that?

#### mind_games

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First of all does the question state that 1g=10 m/(s^2)? or or did you just say that. If the question stated it, then of course use that. Otherwise use the more accurate value of 1g=9.8 m/(s^2) or 9.81 or whatever you've been told to use.

So to get the answer in g's just divide the original answer (47.6190...) by 10 or 9.8 or 9.81 or whatever you've been using.

Which gives you:
4.8 g's if you divide by 10 (ie 1g=10 m/(s^2))
or
4.9 g's if you divided by 9.8

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