HELP MATHS PROBLEM need really smart maths people

hey, got an assignment due VERY soon should have done it earlier was too busy riding.

can anybody please help me work this out.

Task2:

The pilot of a small plane is attempting to land on a small airstrip, and the wheels hit the runway only 1000 metres short of a large group of trees at the end of the runway. The plane’s speed on the tarmac is modeled by the equation v = A-10^kt, where v the plane’s velocity in m/s, t is the time taken n seconds to come to a complete halt and A and K are constants.

graph showing decelleration of plane

If the pilot is attempting to land the plane at a speed of 80m/s,

a. Calculate the value of A (1 mark)
b. 8) investigate at least 3 different values of k between (but not including) 0.01 and 0.2 and for each value determine whether the plane comes to a complete stop before the end of the runway. Use any graphs and/or diagrams, any numerical techniques and any technology t
to support your arguments, justify your procedures. What physical conditions could make k vary? List assumptions you have made. Would there be any values of k (not just the values between 0.01 and 0.2) for which this equation could not be used to model the velocity of a plane landing on a tarmac? Give your reasons and justify your answer

Okay, this is a bit confusing.

Just to verify, is it v = A - 10 to the power of (k times t) or is it v = A - (10 to the power of k) times t? The first one would be very strange and give a very unrealistic graph for deceleration. Is t 0 at touch-down? Could you post the exact wording from the text-book?

Edit: On a second thought, I’m not sure how realistic the graph would be. I guess it depends how the plane decelarates. If it’s by reversing the turbines then it wouldn’t be that bad, I guess.

thats the exact wording on the task sheet.

it is

v = a - (10 ^ kt)

i’m assuming t = 0 at touch down, yes.

You’re a gun at maths, man.

a) I think A will be 81 m/s. V should be 80m/s at touch-down(specified), so.
v = A - 10^kt => 80m/s + 10^(k0) = 81m/s. This would really make much more sense(to me, at least) if it was something like t10^k, but there we are.

yeah for the first part i too got 81 for A

p.s A isnt a speed, it’s just a constant.
now im stuck at the second part

Thanks, man.
You’ll need to integrate to find if it will stop before the end of the runway or use the graphs somehow.

ps. Oh no, Naomi’s reading this thread. Good, she’ll correct me if I’m wrong.

Have you guys done integration? They wouldn’t make you do something that you don’t know how to do. What graphs do they give you?

yes they tought us about it.

no i dont remember any of it.

they ave us a graph that has time down the bonnom, which goes for 16 units, and no label on the y axis. there is a curse from the top left to the bottom right.

I think you shuold get Mawsome to help solve the probelm. Ha ha.

A common attitude seen from a few of my students too. No respect for mathematics at all. :slight_smile:

Deserves to go into one of those lists of exam bloopers.

Nao

hahaha well spotted there naomi.

GOT A QUESTION

how do i use logs to figure out t

81 = 10 ^ 0.02t

if you can help, please do

That’s a good start, although A is not just a constant. Think about it.

Nao

it said it was a constant lol :s.

please help with the log thing. please please please

10^t=x
log(x)=t

So, log(81)/0.02=t

that gives me 95 seconds to stop.

if i investigate 2 other values of k i get"
k = 0.1
t = 19

19 seconds to stop

k = 0.19
t = 10

10 seconds to stop

am i on the right track here?

Yes, I think so. Now you either have to have a graph for each value of k that you’re testing and find the area under it by counting the squares(the old one) or integrate v=A - 10^kt and find the area between t=0 and t when v is 0. I’m still trying to figure out how to integrate the thing, can’t think of a way.

hmmmm.

how do i graph for each value of k

i cant work it out

thats pretty much it, and thats pretty much what i got, except i used different values for k.

now you have to use the simpsons rule to find the area under it, like in task 1.

thats what i still have to do.

Well, you could do it manually. Are you allowed calculators? Or you could also use the trapezium rule to find an estimate. I can’t believe I didn’t think of this before. That’s probably the easiest solution in this situation.