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Mazyrski [523]
3 years ago
14

An elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the ve

locity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is positive.

Mathematics
2 answers:
STatiana [176]3 years ago
6 0

If they appear to be travelling at 8 m/s as viewed by one of them, then someone on ground floor sees what is actually happening. One is going up at 4 m/s and the other is going down at 4 m/s.

The direction matters. The answer is C.

ANTONII [103]3 years ago
5 0
LiftA= u m/s ( upwards)
LiftB= -u m/s(downward)

Velocity A relative to B= V lift A- V lift B=8m/s
u-(-u)=8
u=4m/s
Lift A= 4 m/sec
Lift B= -4m/sec
For someone standing on first floor will be stationary W.r.t to the lift.
V lift A relative to Man= V liftA - V man= 4m/s

V lift B relative to Man= V lift B- V Man= -4 m/s
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Help please calculus
VLD [36.1K]

Let x, y, and z denote the side lengths of the box, with the bottom face having dimensions x-by-y and z is the height. Naturally this means each of x, y, and z must be greater than 0.

The box has a fixed volume of 252 cm³, so

xyz = 252

The surface area of the box is

2xy + 2xz + 2yz

and we're told that the material cost for each face is different. The total cost of the material needed to make the box is given by

C (x, y, z) = ($5/cm²) xy + ($2/cm²) xy + 2 ($3/cm²) (xz + yz)

or, omitting units and simplifying,

C (x, y, z) = 7xy + 6 (x + y) z

In the volume constraint, solve for any one variable; I'll do z.

z = 252/(xy)

Substitute this into the cost function:

C (x, y, 252/(xy)) = 7xy + 1512 (x + y)/(xy)

Since this is now a function of 2 variables, I'll rewrite this as

C* (x, y) = 7xy + 1512 (1/y + 1/x)

Compute the partial derivatives of C and find the critical points:

∂C/∂x = 7y - 1512/x² = 0   ⇒   x² y = 216

∂C/∂y = 7x - 1512/y² = 0   ⇒   x y² = 216

It follows that

x² y = x y²   ⇒   x = y

Just like before, we can think about C* as yet another function but only of 1 variable,

C** (x) = 7x² + 3024/x

Now find the critical points of C** :

dC**/dx = 14x - 3024/x² = 0   ⇒   x = 6

All of this tells us that C (x, y, z) has a critical point when x = y = 6 and z = 252/6² = 7. So the box that costs the least has dimensions 6 × 6 × 7 cm, which gives the box a surface area of 240 cm² and a total cost of $756.

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2 years ago
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Drupady [299]
5/8 9/x

Cross multiply

9x8=72
5×x=5x

Rewrite the equation

72 = 5x

Divide by 5

72÷5=14.4

So, x=14.4
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Anni [7]

Answer:

I think it is 1

Step-by-step explanation:

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babunello [35]

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3 years ago
Evaluate-a-function f(x) = <img src="https://tex.z-dn.net/?f=%5Cfrac%7Bx%7D%7B7%7D" id="TexFormula1" title="\frac{x}{7}" alt="\f
OLga [1]

Step-by-step explanation:

Hey there!

f(x) = 7/x

<em>~ Simply keep the "7" in the place where "x" is there.</em>

f(7) =  \frac{7}{7}

Therefore, X= 1.

<em><u>Hope</u></em><em><u> it</u></em><em><u> helps</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em>

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3 years ago
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