formulas and applications

D

devasquez10

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The formula D = 16t2 is used to approximate the distance in feet an object falls in t seconds. A package is dropped from an airplane that is 6400 feet above the ground. How many seconds elapse before it hits the ground?



16t squared not 2
 
devasquez10 said:
The formula D = 16t2 is used to approximate the distance in feet an object falls in t seconds. A package is dropped from an airplane that is 6400 feet above the ground. How many seconds elapse before it hits the ground?
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Hint:

1) What do you need to find? How many seconds elapse before it hits the ground - time

2) Assign a variable name to it? Let t = time

Continue.....

Please share your work/thoughts with us - so that we know where to begin to help you.
 
Subhotosh Khan said:
No .... No ... Double No.

Look at the given equation again!

What happened to the exponent of 't'?

What happened to 16?

Try again......
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Sorry, I read the problem wrong and I forgot to put the 1 in front of the 6 and square it. I am so confused so D=16t2 (squared). t=time. Ok. Is the distance 6400 of how far it dropped? I am just confused about how to set this equation up. I tried 16(60)t2 and D=16t2 + 60x. I got the 60 from how many seconds are in a minute but I know this is wrong because I get crazy big numbers....
 
devasquez10 said:
… Is the distance 6400 [how] far it dropped? …
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Hello devasquez. Yes. The object was dropped at 6400 feet above the ground, so it falls 6400 feet. In the formula D=16t^2, symbol D represents the falling distance in feet.

… confused about how to set this equation up. I tried 16(60)t2 and D=16t2 + 60x …
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Don't set up new formulas. Use the formula they gave you and substitute the value 6400 for symbol D:

16t^2 = 6400

Now solve for t and ignore the negative solution.

… I got the 60 from how many seconds are in a minute …
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You don't need to convert anything to minutes. The exercises asks for a number of seconds and symbol t represents that time in seconds, so the positive solution for t above is the answer. Cheers!

PS: When typing, we show exponents using the caret symbol ^

?
 
Thanks so much Otis for explaining that! So, I did 16^2 which is 256 and then I divided 6400 by 256 which gets me t=25. Is that correct.? I have an answer key which says 20 seconds but that has to be wrong.
 
devasquez10 said:
Thanks so much Otis for explaining that! So, I did 16^2 which is 256 and then I divided 6400 by 256 which gets me t=25. Is that correct.? I have an answer key which says 20 seconds but that has to be wrong.
Click to expand...
Yes it is wrong!

Why 16^2?

The "^2" is associated with "t"! Not with 16.

This should be:

16 * t2 = 6400 .... divide both sides by 16 to isolate "t".

t2 = 6400/16 = 400

t = (400)1/2

Continue......
 
Where did t^2 go? Did you multiply by 1/2 on each side ? And (400)1/2 isn’t that 200?
 
devasquez10 said:
Where did t^2 go?
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Did you multiply by 1/2 on each side ? - No! I took "square root" of both sides. That is also expressed as "^(1/2)" or "(1/2)" or "√"

And (400)1/2 isn’t that 200? - no it is (400)1/2 or √(400) which is equal to 20 (Book's answer).
 
Oh ok I understand now, that was way more simple than I thought. Thank you for taking the time to explain it!
 
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