Jet Plane Acceleration: 400 m/s in 4.0 km

[oldunion]

A jet plane is cruising at 300 m/s when suddenly the pilot turns the engines up to full throttle. After traveling 4.0 km, the jet is moving with a speed of 400 m/s.

assuming a constant acceleration, what is it. answer is in m/s^2

I am not seeing how this is done without using time. also as a general question. i have no problem with math because it is logical and you have equations to solve it. but physics, i am constantly lost. am i to use known equations or do i have to make things up?

 

[cepheid]

I don't get it. Why would you just...make things up? They would be wrong.

In problems like this, always always always list the given quantities so that you know what information you have to work with. In this problem:

v_0 = 300 \text{m/s}

v = 400 \text{m/s}

d = 4000 \text{m}

a = \text{const.}

Now, ask yourself: I have the initial and final velocities, the acceleration (to solve for), and the distance travelled. For motion in a straight line with constant acceleration, is there some relationship that relates these quantities? The answer should be a resounding yes. You have no doubt derived in class a kinematical formula expressing the final velocity in terms of the initial velocity, acceleration, and the distance traveled (over the course of that change in velocity).

 

[oldunion]

haha, I am afraid you have the idea of my class all wrong. he will look at this projector the whole time and personally do 2 or 3 problems leaving everyone clueless. thus, i learn physics from this book I am looking at and a workbook. so I am teaching myself more or less.

i have (400m/s)^2=(300m/s)^2+2a4000

a=8.75m/s^2 correct?

 

[vincentchan]

haha, I am afraid you have the idea of my class all wrong. he will look at this projector the whole time and personally do 2 or 3 problems leaving everyone clueless. thus, i learn physics from this book I am looking at and a workbook. so I am teaching myself more or less.

i have (400m/s)^2=(300m/s)^2+2a4000

what did you mean...are you saying the answer is what you just said...
you and cepheid are completely correct

 

[oldunion]

i was guessing, is the answer (8.75m/s)^2?

 

[vincentchan]

did I tell you that you and cepheid is completely correct?

 

[oldunion]

what did you mean...are you saying the answer is what you just said...
you and cepheid are completely correct

yes, but i don't see my answer quoted. thank you for your help