The problem of changing parts and calculating density in Physics About changing parts for machine, finding the weight or density of parts, the more the better

1. In order to reduce the gravity of the aircraft, a steel part is replaced by an aluminum part to reduce its mass by 104kg. What is the mass of aluminum required? A: 54kg2. In a factory, the density of 0.9 * 10 ^ 3kg / m ^ 3 plastic is used to replace the density of 7.9 * 10 ^ 3 iron part to reduce its mass by 14kg

Two math problems in grade one of junior high school
1. Given that 2 ^ 48 - 1 can be divided by two integers between 60 and 70, what are the two integers?
2. Given (a + B-3) ² + (a-b + 5) ² = 0, find the value of a & #178; - B & #178

2 ^ 48-1 = (2 ^ 24 + 1) (2 ^ 24-1) = (2 ^ 24 + 1) (2 ^ 12 + 1) (2 ^ 12-1) = (2 ^ 24 + 1) (2 ^ 12 + 1) (2 ^ 6 + 1) (2 ^ 6-1) = (2 ^ 24 + 1) (2 ^ 12 + 1) * 65 * 63, so the two numbers are 65 and 63, because (a + B-3) & sup2; + (a-b + 5) & sup2; = 0, so a + B-3 = 0a-b + 5 = 0, so a + B = 3, A-B = - 5, so a & sup2; - B

The focus coordinate of parabola x ^ 2-4y-2 = 0 is
Please take the process with you

Parabola x ^ 2-4y-2 = 0
That is X & # 178; = 4Y + 2
That is X & # 178; = 4 (y + 1 / 2)
The vertex of the parabola is (0, - 1 / 2), with the opening upward,
The focal distance is p = 2
The focus coordinate is (0,1 / 2)

Calculation of cylinder weight
It is known that the length of the cylinder is 190 cm and the cross section is 80 cm!
How can I calculate the weight of the object?
The density is 0.00617
|-----------Total length 190----------|
------------------------------ -
|___ _ | 12.5 |
| | |
50 | same on both sides | 50 80
| |_ |
------ |
|____________________________ | 12.5 -
|--------160--------|
The drawing is a little bad. What's the weight of this one?
How did this happen,

Density = mass / volume
Cylinder volume = base area * height
Here, the cross section is equivalent to the bottom area = 80 square centimeters
Mass = density * Volume
As for the picture you drew, it's a little difficult to understand. Sorry

A simple operation problem in Mathematics
Each student needs to use 9 exercise books. There are 42 students in class 4 (1) and 39 students in class 4 (2). How many stupid exercise books do these two classes need? How would you calculate?

（42+39）9=81*9
=（80+1）*9
=720+9
=729
A: a total of 729 copies are required

Let f (x) = a (x-1), G (x) = (x + b) LNX (a, B are real numbers, and a > 0) (1) find g (x)
Let f (x) = a (x-1), G (x) = (x + b) LNX (a, B are real numbers, and a > 0)
(1) Find out that G (x) is a monotone increasing function in its domain of definition, and find out the value range of B

G (x) = (x + b) LNX, domain of definition (0, + ∞),
g'(x)= lnx+(x+b)/x
G (x) is a monotone increasing function in its domain,
When x > 0, G '(x) ≥ 0
That is LNX + (x + b) / X ≥ 0,
（x+b)/x≥-lnx
B ≥ - xlnx-x is constant,
Let H (x) = - xlnx-x,
B ≥ H (x) max
h'(x)=-lnx-2
Let H '(x) = 0, LNX = - 2, x = 1 / e ^ 2
When 0

How many cm is one cubic meter
How many cm is one cubic meter by sea
What is the height, width and length

100*100*100cm

Specified operation: a * b = 5A + 2b-1, then the value of 4 * B is
I don't know what symbol (+). -. Here are four answers. Pick them out and help me write the process. A.37 b.31 c.41 d.27 urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent urgent

What is the formula for calculating the volume of a sphere? We still need to teach it. Can we express it in letters
What about words
I can't read the letters. It's a sphere

Sphere volume formula V sphere = (4 / 3) * Pai * R ^ 3

Vega is about 27 light-years away from the earth. How many meters is Vega away from the earth

One light year is equal to the distance light travels in one year:
1*365*24*3600*（8*10＾8）m=2.5*10^16m
27 light years is equivalent to:
27*2.5*10^16m＝6.75*10＾17m

The problem of changing parts and calculating density in Physics About changing parts for machine, finding the weight or density of parts, the more the better