Question

The height of a rocket at different times after it was fired was 50.0m at 0s, 65.1m at 1s, 70.4m at 2s, 65.9m at 3s, 51.5m at 4s, and 27.5m at 5 seconds. How long will the rocket stay in the air?

Answer 1

what are you studying right now?

Answer 2

Multiple representations of functions.

Answer 3

many ways to solve this, I still don't have any idea what you're studying, so I'll just assume you're in pre-calc. or something and are learning about parabolas..

Answer 4

o sorry, it's algebra 2.

Answer 5

fixt.

Answer 6

I don't quite get what you mean. I can send a pic of the problem tho?

Answer 7

sure

Answer 8

part A and B are simple, I just don't know how to do Part C

Answer 9

cool. what did you get for A?

Answer 10

I graphed it

Answer 11

assuming that's right of course. lol

Answer 12

how...

Answer 13

And B is clearly 70.4

Answer 14

you graphed the points and ran some utility that did a quadratic fit or something?

Answer 15

I doubt B is 70.4

Answer 16

O no, I thought it was asking the best way to show the data, so my answer was to graph it. But I didn't actually do that.

Answer 17

So could you help me, cause I clearly don't know how to do it? lol

Answer 18

h = at^2 +bt +c
at t= 0 h=50 so c=50

at t=1, h=65.1 so
65.1 = a +b +50

at t=2, h=70.4m so
70.4 = 4a +2b +50

solve for a and b and you have h(t)
use it to find t when h(t) =0

Answer 19

I'm so lost. what does this mean?

Answer 20

you have learned about parabolas right?

Answer 21

yes

Answer 22

general form for a parabola is y =ax^2 +bx +c

Answer 23

right?

Answer 24

this is a parabola...

Answer 25

they want you to use some or all of the points they gave you in order to find the equation of this parabola...

Answer 26

How do we do that?

Answer 27

h = at^2 +bt +c

Answer 28

plug them in

Answer 29

when t=0 h=50

Answer 30

50 = a*0 + b*0 +c

Answer 31

c=50

Answer 32

when t =1 h =65.1

65.1 = a*1 +b*1 +50

Answer 33

when t =2 h =70.4

70.4 = a*2^2 +b*2 +50
70.4 =4a + 2b +50

Answer 34

you can find a and b now, so you know what the answer to part A is... (you have an equation that models the height of the rocket as a function of time)

Answer 35

How do I find a and b in this equation?

Answer 36

solve simultaneous equations:
65.1 = a +b+50
70.4 =4a + 2b +50

Answer 37

but how do I solve this without knowing a or b?

Answer 38

don't know.

Answer 39

probably by using a calculator that does quadratic fitting.

Answer 40

I just started this class. How on earth could it be this complicated?

Answer 41

Sorry, but I think I'll find help elsewhere

Answer 42

I think they want you to actually find the equation on your own however... since the other way is not really a test of anything but whether or not you have a quadratic fitting program on your calculator.

Answer 43

oh noes.