Question

can someone check my work on my previous post about the 420 pounds? can someone check my work on my previous post about the 420 pounds? @Mathematics

Answer 1

can you post the link?

Answer 2

if you scroll down some in the room its still showing as posted :)

Answer 3

i will post it here

Answer 4

an object is 420 pounds when it is at sea level. Find the value of C that makes the equation true. (Sea level is 3,963 miles from the center of the Earth.) can someone help me work this out please I dont understand any of it

Answer 5

ive got that part figured out I think its just the rest of it

Answer 6

It seems we are missing some context here. What kind of problems have you been doing in class? Physics, linear equations, proportions, etc?

Answer 7

we are doing like the square root, im new to it all

Answer 8

w=Cr^-2

Answer 9

Ahhhhhh the equation!

Answer 10

that makes this doable.

Answer 11

so I have w=420(3963)^-2

Answer 12

your equation is

w=Cr^-2

now which variable represents which number?

Answer 13

w=420(15705369)
w=6596254980

Answer 14

I mean

w=?
r=?
C=?

what does each variable represent?

Answer 15

the weight of an object follows this equation: , where C is a constant, and r is the distance that the object is from the center of Earth.

Answer 16

so r would be 3963?

Answer 17

I'm sorry, I have no idea how you got that number.

As to your previous comment you are right. So then which number do we
NOT know and need to find out

Answer 18

?

Answer 19

That is, which numbers do we know, and which do we not know.
Do we know the value of r?
Do we know the value of C?

Answer 20

maybe i have confused you lol let me do it like this...
the weight of an object follows this equation: , where C is a constant, and r is the distance that the object is from the center of Earth.

Solve the equation for r.
. Suppose that an object is 420 pounds when it is at sea level. Find the value of C that makes the equation true. (Sea level is 3,963 miles from the center of the Earth.)

Answer 21

1 mile = 5,280 feet

Answer 22

can you see why i have no clue what im doing lol

Answer 23

why do you think you need to solve for r?
In math we solve for the variable we do NOT know the value of, in this case C. We need to find what value of C makes the statement above true, which is done by solving for C:

w=Cr^-2
C=wr^2

now plug in the values for w and r and this equation will give you C

Answer 24

oh so i needed to multiply or something to get it in that form?

Answer 25

c=420(3963)^2

Answer 26

yes, the operation to go from

w=Cr^-2--->C=wr^2

is that we multiplied both sides by r^2

w(r^2)=Cr^(-2)(r^2)
wr^2=C

if you understand adding exponents this should make sense

yes C=420(3963)^2=659625980

I am not sure of the units, but that is the number

Answer 27

. Now i Use the value of C i found in the previous question to determine how much the object would weigh

In Moscow, Russia (450 feet above sea level).

Answer 28

did you give up?

Answer 29

soo 65962598(3963-450/5280)^2

Answer 30

no im still working on it lol

Answer 31

ok cool

Answer 32

I can give hints if you want

Answer 33

65962598(3962.9148)^2
65962598(15704655.6681

Answer 34

if you can just see if im doing it right and just help me work it out would be fine

Answer 35

i just dont think what im doing is right though

Answer 36

I'm sorry but you're quite far off. Our equation is

\[w=Cr^{-2}={C \over r^2}\]

we know r in moscow (it's r at sea level plus 450)
and after our last problem we know C

so which numbers are we going to plug in?

Answer 37

450 and 3963?

Answer 38

no thats not right

Answer 39

correct so where and what is the answer?

Answer 40

oh it is right lol

Answer 41

w=450(3963)^2?

Answer 42

I', sorr, those number are correct for the new r, (that is r of moscow)

in moscow, r=3963+450

AND we need to plug in C to the right place. My fault gor not mentioning that.

So what is the answer?

Answer 43

4413

Answer 44

dont i have to divide the 450 into the 5280?

Answer 45

im sorry my connection is bad and this server is as well one moment, it's on paper but hard to type

Answer 46

what if i emailed you the sheet so you can look at it ans see what im talking about. I feel like ive confused you a ton lol

Answer 47

wait i can do it here i think

Answer 48

\[w={C \over r^2}\]\[C=w r^2=420(3963)^2\]
for moscow

\[w={C \over r_m2^2}={420*3963^2\over(3963+450)^2}=338.2\]I'm sorry this answer must be wrong and makes no sense. It's very late where I am and I'm more tired than I thought. I'll help you next time I promise.

Answer 49

): goodnight...

Answer 50

goodnight

Answer 51

thanks for the help though