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makvit [3.9K]
3 years ago
13

After t seconds, a ball tossed in the air from the ground level reaches a height of h feet given by the equation h = 144t-16t^2

Mathematics
2 answers:
lesantik [10]3 years ago
4 0
144t-16t^2= 16t(9-t)
after 3 seconds (just substitute t=3):
16(3)(9-3)=
16(3)(6)=
16*18=
288
maximum height: find the average of the roots:
the roots of 16t(9-t) are t=0 or t=9
since it's a parabola, the maximum is at t=4.5, at 324 ft
if its height is 224 feet, the equation is 224=144t-16t^2
16t^2-144t+224=0
divide by 16: t^2-9t+14=0
this can be factored as (t-2)(t-7)=0
the roots are t=2 and t=7, so the ball has been in the air for either 2 seconds or 7 seconds
the roots to 144t-16t^2 are 0 and 9, so the ball will hit the ground 9 seconds after being thrown
kaheart [24]3 years ago
4 0
H = -16t^2 + 144t
when you substitute a number in for t, it will tell you how high in the air the ball is after that many seconds. to find the height at three seconds, put in 3 for t.
h = -16*9 + 144*3
h = -144 + 3*144
h = 2*144 (i didn't want to multiply out 3*144 cause im lazy, so i combined like terms as if 144 was a variable.)
h = 288
after 3 seconds, the ball is 288ft in the air.

the maximum height is more complicated (and feel free to skip this paragraph if you think it'll confuse you more.) you could do it with a graphing calculator by graphing the function f(x)=-16x^2+144t and using a maximum feature. you could also use differential calculus to find it. but i think the best way is the way suggested by the person who answered before me, that is, finding the average of the roots. since the parabola's line of symmetry is perpendicular to the x-axis, that means the places the parabola intersects the x-axis (the roots) will be the same distance from the axis of symmetry and therefore the same distance from the vertex (the maximum point of the parabola.)

the roots of the parabola can be found this way:
h = -16t^2 + 144t
0 =  -16t^2 + 144t
0 = t(-16t + 144)
0 = t or 0 = -16t + 144
16t = 144
t = 9
the roots are t=0 and t=9, therefore the line of symmetry (the middle of the parabola) is t=4.5. to find the maximum point of the parabola, plug 4.5 into the function for t and find the resulting height.
h = -16(4.5)^2 + 144(4.5)
h =  -324 + 648
h = 324
so the maximum height happens at t=4.5 seconds, and the maximum height is 324ft.

to find how long it takes for the ball to be at 224 feet in the air, substitute 224 in for h:
h = -16t^2 + 144t
224 = -16t^2 + 144t
56 = -4t^2 + 36t divide by 4
14 = -t^2 + 9t divide by 4 again
t^2 - 9t + 14 = 0 rearrange
(t - 7)(t - 2) = 0
t = 7 and t = 2
at 2 seconds and again at 7 seconds, the ball will be 224ft in the air.

after how many seconds will the ball hit the ground? we already know this. the ball touches the ground just like the parabola touches the x-axis. to find when the ball hits the ground, we just have to find the root of the parabola, and we already know from earlier that the roots are t=0 and t=9. so, the ball will come into contact with the ground at 9 seconds.

hope this helped
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Doogle drove 30 and one-third miles toward his brother's house in one-third of an hour. About how long will the entire 100-mile
Olenka [21]

Answer:

1\frac{9}{91}\ hours

Step-by-step explanation:

we know that

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30\frac{1}{3}\ mi=\frac{30*3+1}{3}=\frac{91}{3}\ mi

one-third of an hour is equal to

\frac{1}{3}\ h

Applying proportion

\frac{(1/3)}{(91/3)}\frac{h}{mi}=\frac{x}{100}\frac{h}{mi}\\ \\x=\frac{100}{91}\ h

Convert to mixed number

\frac{100}{91}\ h=\frac{91}{91}+\frac{9}{91}=1\frac{9}{91}\ h

8 0
3 years ago
Read 2 more answers
Let t be time in seconds and let r(t) be the rate, in gallons per second, that water enters a reservoir: r(t)=700−40t. a) For 0≤
Flura [38]
What you don't want is the value of r(t) becoming negative. Surely that would represent water escaping the reservoir.

How big can (t) get before water actually starts escaping the reservoir?

Essentially, to figure this out r(t) would have to be equal to 0. 

700 - 40t = 0

40t=700

t=700/40=17.5

So the first answer is 17.5 seconds. After this amount of time has elapsed the reservoir will start to lose water as r(t) would become negative.

---------------

The reservoir had the least amount of water in it before it was being filled. That was when t=0. The volume of water in the reservoir wasn't negatively impacted as not enough water had escaped it during the 17.5 to 30 second period.
7 0
3 years ago
Help, and if you can give me a step by step explanation
Llana [10]

Answer:

the first option

Step-by-step explanation:

variability !

what does that word tell us ?

it means that there are more individuals differences.

you could also use "accuracy" as the opposite - we are aiming for the mean value ...

imagine some bow and arrow tournament.

who wins ?

the person with the highest accuracy across all the attempts (and that means the lowest variability in the results across all attempts relatively to the target center representing the predefined mean value).

now look at the graphic for neighborhood A.

and then for neighborhood B.

which one has the data points more clustered around the center (where the mean value is going to be) ? this one has lower variability than the one where the data points are having more than one cluster or are even all over the place.

remember, for the variability you have to add all the differences to the mean value. the smaller the differences to the mean value, the smaller the variability.

in neighborhood B almost all data points have a larger difference to the mean value.

so, the variability will be higher here.

5 0
2 years ago
Petrolyn motor oil is a combination of natural oil and synthetic oil. It contains 7 liters of natural oil for every 5 liters of
Svetach [21]
What we know:
Petrolyn motor oil is a combination of natural oil and synthetic oil. It contains 7 liters of natural oil for every 5 liters of synthetic oil.

What we need to find:
If 355 liters of synthetic oil are used, how many liters of petrolyn oil will be made?

Set up a proportion to find how much natural oil is used.
7L natural oil/5L synthetic oil = x/355 synthetic oil where x=natural oil
7/5=x/355
(5)(x)=(7)(355) cross multiplied
5x=2485 simplified
5/5x=2485/5 multiplicative inverse
x=497L

Now, add both synthetic oil and natural oil to find amount of petrolyn oil.

355 L synthetic oil + 497 L natural oil= 852 L of petrolyn oil
5 0
3 years ago
What’s the value of this expression?
yaroslaw [1]

Answer:

ans is 0

Step-by-step explanation:

(3/5)0×-2

(3/5)^0

so the answer Is 0

8 0
3 years ago
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