1. What is the buoyancy of a 60m4 helium balloon? (air density is 1.29Kg / m3, G is 10N / kg) 2. The buoyancy of an object submerged in water is 50N. What is the buoyancy of an object submerged in alcohol? (alcohol density is 0.8g / cm3, G is 10N / kg) 3. What is the buoyancy of a 270 gram aluminum block when half of its volume is immersed in water? (the density of aluminum is 1.29 kg / m3, 10N / kg for G)

1. What is the buoyancy of a 60m4 helium balloon? (air density is 1.29Kg / m3, G is 10N / kg) 2. The buoyancy of an object submerged in water is 50N. What is the buoyancy of an object submerged in alcohol? (alcohol density is 0.8g / cm3, G is 10N / kg) 3. What is the buoyancy of a 270 gram aluminum block when half of its volume is immersed in water? (the density of aluminum is 1.29 kg / m3, 10N / kg for G)

As shown in the figure, the front view and the left view of a space geometry are equilateral triangles with side length of 1, and the top view is a circle, then the side area of the geometry is ()
A. π4B. 24πC. 22πD. 12π

According to the title, the direct view of the geometry is a cone with a bottom radius of 12 and a generatrix length of 1. Its side expansion is a sector with an arc length of 2 π r = π, and the side area of the geometry is s = 12 π × 1 = π 2, so D is selected

Find the area of the triangle formed by the tangent line and two coordinate axes at any point P on the hyperbola y = 1 / X

Let P (x1,1 / x1)
P point tangent slope k = (1 / x) '= - 1 / (x1 ^ 2)
Tangent equation Y-1 / X1 = - 1 / (x1 ^ 2) * (x-1 / x1)
X = 0, the intercept on the Y axis is y2 = 2 / x1
Y = 0, the intercept on the x-axis is x2 = 2x1
S=1/2*|x2y2|=2

What is the difference between concrete grade C15, C20 and C25?
Is the higher the label, the greater the strength?

C15, C20, C25, etc. are the strength grades, and the label is the former name
For example, C20 refers to the standard curing block of concrete. When the age is 28 days, the standard value of compressive strength is 20 MPa
So the bigger the label, the higher the intensity is right

Use square difference and complete square formula to solve equation: (2x-1) square-5 = 0

Solution
(2x-1)^2-5=0
Square difference
(2x-1+√5)(2x-1-√5)=0
∴2x-1+√5=0
Or 2x-1 - √ 5 = 0
∴x=(1-√5)/2
Or x = (√ 5 + 1) / 2
Or with
(2x-1)^2-5=0
(2x-1)^2=5
∴2x-1=±√5
∴x=(1+√5)/2
Or x = (1 - √ 5) / 2

What is the negative 2 / 3 power of 8? How to write the calculation process

8^(-2/3)
=1/[8(2/3)
=1 / [(8 to 3) ^ 2]
=1/(2^2)
=1/4
I've checked it with a calculator. I'm sure it's right

Is density related to mass and volume?
If not, why do we use mass and volume to calculate density?
So where does density have to do with mass and volume?

The physical meaning of density is a property of matter, which does not change with the change of mass and volume, but only with the change of state (temperature and pressure). The ratio of the mass of a substance to its volume, that is, the mass of a substance per unit volume, is called the density of this substance

101²+99²=

a²+b²=（a+b）²-2ab
Original formula = (101 + 99) ² - 2x101x99
= 40000-19998
=20002

Given that the vertex is at the origin and the focus is on the x-axis, the parabola passes through the point (1,2), the standard equation of the parabola is solved

The parabola with vertex at origin and focus on X axis is set as y ^ 2 = 2px
If passing through point (1,2), then 4 = 2p * 1, P = 2
The parabolic equation is y ^ 2 = 4x

The piston area of a single cylinder gasoline engine is 120cm2, the piston moving distance in the power stroke is 30cm, the average pressure of gas is 5 × 105Pa, the calorific value of gasoline is 4.6 × 107j / kg, the power consumption of each fuel is 0.2g, the gas is once
If 90% of the gasoline is completely burned in the process of doing work each time, what is the heat released by each gasoline combustion
yaoguocheng

The piston area of a single cylinder gasoline engine is 120cm2, the piston moving distance in the power stroke is 30cm, the average pressure of gas is 5 × 105Pa, the calorific value of gasoline is 4.6 × 107j / kg, the power consumption of oil is 0.2g each time, and the work of gas expansion on the piston is (1800j); if 90% of the gasoline is completely burned in each power stroke, the fuel consumption is 0.2g each time, The heat released by each gasoline combustion is (8280j); in the exhaust process, the exhaust gas temperature (reduced), the internal energy (reduced)
W = FL = PSL = 5 × 10 ^ 5pa * 0.012m2 * 0.3m = 1800j -------- work = force x distance force = pressure x area
Q = MQ * 90% = 0.0002kg * 4.6 × 10 ^ 7J / kg * 90% = 8280j -------- complete combustion does not need to multiply by 90%