Question

if a rock is thrown upward with an initial velocity of 64ft per second from the top of a 25-foot building write the height(s) equation using this information, how high is the rock after1 second after how many seconds will rock reach max

Answer 1

can u please help

Answer 2

what's the attachment for?

Answer 3

theres graph on there i dont understand

Answer 4

ok, i'll look at your first question for now...

Answer 5

also
okay thankyou

Answer 6

Alright, the way I learned it the height equation is:

h(t) = v*t -4.9t^2

Do you have a different version? Just want to use what's familiar to you.

Answer 7

Actually, you might have

h(t) = v*t - 16t^2

since you're using ft/sec

Answer 8

Let me know if you have a different formula cuz that will change the answer

Answer 9

no thats it
of 64ft per second from the top of a 25

Answer 10

ok, so we start from a height of 25 ft. That means we must adjust the equation to become:

h(t) = v*t - 16t^2 + 25

That + 25 will ensure that at t = 0, h(t) = 25 like we want.

Answer 11

Now you know what v is, since that is just the speed that you throw it at initially. In other words, v = 64 ft/sec.

Answer 12

Thus, we have:

h(t) = 64t - 16t^2 + 25

or to make it look nicer algebraically..

h(t) = -16t^2 + 64t + 25

Answer 13

Now, do you think you can find what the height is after 1 second?

Answer 14

yes
im just adding1 to equation right

Answer 15

yes, if you mean you are plugging in t = 1. So, make all the t's into 1's. :)

Answer 16

t is just the time

Answer 17

ok then i substitute16 right

Answer 18

Well, you should get this:

h(1) means the height at 1 second, so:

h(1) = -16(1)^2 + 64(1) + 25

Answer 19

solve the right side and what do you get?

Answer 20

-48

Answer 21

ok, that's not quite it, what calculations did you do?

Answer 22

16^2

Answer 23

ok, the ^2 only affects the 1

Answer 24

the equation is -16t^2 not -(16t)^2, which is a big difference. the exponent only effects the time

Answer 25

so, it's easier than what you thought cuz it's just 1^2 which is 1

Answer 26

so -16(1)^2 = -16. if you use that what does your answer become?

Answer 27

0

Answer 28

if i divide 16/16right

Answer 29

oh.. you don't have to divide by 16

Answer 30

okay

Answer 31

it's just straight up addition of -16(1)^2 + 64(1) + 25

Answer 32

so that's just -16 + 64 + 25

Answer 33

or 73, does that make sense? :)

Answer 34

ok

Answer 35

So the height after 1 second is 73 feet. And we got that by plugging in t = 1 into
h(t) = -16t^2 + 64t + 25.

Answer 36

ok, how would i solve for the graph

Answer 37

are you referring to the one about Bob's salary?

Answer 38

yes

Answer 39

ok, so the horizontal line is always your x, and the vertical line is always your y.

Answer 40

ok, so would it be 2,4,6,8=230,000or270000 because it seem like its go by2

Answer 41

are you doing part a) or which part are you on?

Answer 42

parta

Answer 43

of the graph it's confusing

Answer 44

ok, so we just need to pick two coordinates. Let's do the first one.

Here's one answer (0, 41000) because when x = 0 on the horizontal line, the graph is at 41000 on the vertical line.

Answer 45

I'm reading between the lines to get the 41000 number, it's between 40000 and 42000.

Answer 46

So how about at x = 2 on the horizontal line, where is the graph vertically at that point?

Answer 47

46000

Answer 48

exactly! So we write (2, 46000).

Answer 49

ok

Answer 50

for linear equation how would i write that, try to take tutoring but my headphones are broken and is lost

Answer 51

Alright, so I'm assuming you already found the slope right? Because you can't write a linear equation without the slope.

Answer 52

no

Answer 53

OK, so we'll start there first :)

Answer 54

okay

Answer 55

So, do you remember or have the definition of slope?

Answer 56

in up right addneg down

Answer 57

x=0

Answer 58

ok, good. so we go up from 41000 to 46000 on the graph and go over from 0 to 2.

Answer 59

Slope = rise / run

or you can think of it as

Slope = (up down) / (left right)

Answer 60

So our slope is 5000 up / 2 right which is 5000/2 = 2500.

Answer 61

that's it for slope

Answer 62

ok

Answer 63

Now to write a linear equation, it will look like this formula:

y = m*x + b

m is the slope, b is the y-intercept (the value of y when x = 0).
When writing a linear equation you just leave x and y alone in the formula.

Answer 64

We already know that m = 2500 and we know that y is 41000 when x = 0, so the b = 41000.

Answer 65

Then, our linear equation is y = 2500x + 41000.

Answer 66

and we are done.

Answer 67

ok

Answer 68

can u look at the next one then thats it

Answer 69

sure

Answer 70

At the beginning of the question they told us that x = 0 was 2002.

Answer 71

so what would x = ? in 2008

Answer 72

23000or0

Answer 73

that might be the salary, but that's the vertical line. Horizontally, we have x = 0 is 2002, x = 1 is 2003, x = 2is 2004... so x = 6 is 2008 right?

Answer 74

yes

Answer 75

so his salary is given by y = 2500x + 41000, which is what we did all the hard work for earlier.

Answer 76

To figure out what his salary will be in 2008 then, we just plug in x = 6

Answer 77

i wasnt sure ok

Answer 78

ok

Answer 79

so that is y = 2500(6) + 41000

Answer 80

and that is 56,000

Answer 81

so,that's how i would do the steps thanku

Answer 82

yep, no problem