What is the meaning of MGH = (1 / 2) MV ^ 2? What is the grade of physics book? In which chapter

What is the meaning of MGH = (1 / 2) MV ^ 2? What is the grade of physics book? In which chapter

Law of conservation of mechanical energy
mgh=mV²/2
Senior one physics

The problem of the formula q = cm Δ t
Now we study the heat released by sodium hydroxide when it is dissolved in water. Using the formula q = cm Δ T, do m here refer to the mass of solute, solvent water or solution?

Strictly speaking, it is the quality of the solution;
It depends on whether you use the specific heat of water or the specific heat of solution in C? This is the corresponding
It is generally believed that NaOH solute will not affect or slightly affect the specific heat of water, but not necessarily other solutes. So here, C is calculated according to water, M is calculated according to solution, because you not only give the heat to water, but also the solute, and its temperature changes. This is approximate calculation

What formula is p = MGH / T? What do P, m, G, h and t stand for? What are their units?

Obviously
M mass, G acceleration of gravity, H height difference between the beginning and the end of the object, t time for the object to fall from 0
MGH is the work done by gravity, compared with T, that is, the power of gravity in 0 ~ t time
P = MGH / T, the unit of P is w, Watt

2 (0.3x + 4) - 5 (0.2x-7) = 9 equation solution

2(0.3X+4)-5(0.2X-7)=9
0.6x+8-x+35=9
0.4x=34
x=85

There is a rectangle whose length and width are reduced by 5 cm each, and the area of the rectangle is reduced by 100 square meters. What is the circumference of the original rectangle?
emergency

Because the length and width are reduced by 5 cm and the area is reduced by 100 square cm
Minus 5 * 5 = 25 square centimeters
5 * (original length-5 + original width-5) = 100-25
Original length + original width = 25 cm
So the circumference of the original rectangle is 25 * 2 = 50 cm

Mathematical problem with a 96 cm long wire welded into a cuboid frame, so that the ratio of length to width is 3:2:1, find the cuboid volume represented by this frame

Length + width + height = 96 △ 4 = 24 (CM)
Length = 24 ÷ (3 + 2 + 1) × 3 = 12 (CM)
Width = 24 ÷ (3 + 2 + 1) × 2 = 8 (CM)
Height = 24 ÷ (3 + 2 + 1) × 1 = 4 (CM)
Volume = 12 × 8 × 4 = 384 (cm3)

Solve equation 4x-2 (8 + x) = 50%

4x-2(8+x)=50%
4x-16-2x=0.5
4x-2x=16+0.5
2x=16.5
x=8.25

On a rectangular cardboard with a length of 8cm and a width of 6cm, how many discs can be cut with a diameter of 2cm?

8 △ 2 = 4 (pieces); 6 △ 2 = 3 (pieces); 4 × 3 = 12 (pieces); answer: at most 12 round iron plates with a diameter of 2 cm can be intercepted

Mathematics formula of Jiangsu Education Press for grade 1-6 of primary school (expressed in letters)

Fundamentals of Mathematics
1、 Calculation formula of perimeter area volume of primary school mathematics geometry
Circumference of rectangle = (length + width) × 2 C = (a + b) × 2
Perimeter of square = side length × 4 C = 4A
Area of rectangle = length × width s = ab
Area of square = side length × side length s = A.A = a
Area of triangle = bottom × height △ 2 s = ah △ 2
Area of parallelogram = base × height s = ah
Area of trapezoid = (upper bottom + lower bottom) × height △ 2 s = (a + b) H △ 2
Diameter = radius × 2 D = 2R radius = diameter △ 2 r = D △ 2
Circumference of circle = circumference × diameter = circumference × radius × 2 C = π d = 2 π R
Area of circle = circumference × radius × radius
The area of triangle = base × height △ 2. Formula s = a × h △ 2
Square area = side length × side length formula s = a × a
The area of rectangle = length × width formula s = a × B
The area of parallelogram = base × height formula s = a × H
Area of trapezoid = (upper bottom + lower bottom) × height △ 2 Formula s = (a + b) H △ 2
Sum of internal angles: sum of internal angles of triangle = 180 degrees
Cuboid volume = length × width × height formula: v = ABH
Cuboid (or cube) volume = base area × height formula: v = ABH
Volume of cube = edge length × edge length × edge length formula: v = AAA
The formula of circle circumference = diameter × π: l = π d = 2 π R
The area of circle = radius × radius × π formula: S = π R2
Surface (side) area of a cylinder: the surface (side) area of a cylinder is equal to the circumference of the bottom multiplied by the height. Formula: S = ch = π DH = 2 π RH
Surface area of a cylinder: the surface area of a cylinder is equal to the circumference of the bottom multiplied by the height plus the area of the circles at both ends. Formula: S = ch + 2S = ch + 2 π R2
Volume of cylinder: the volume of cylinder is equal to the area of bottom multiplied by height. Formula: v = sh
The volume of the cone is 1 / 3 of the bottom surface × the product height. The formula is v = 1 / 3SH
The law of addition and subtraction of fractions: the fractions with the same denominator are added and subtracted, only the numerator is added and subtracted, and the denominator is not changed. The fractions with different denominators are added and subtracted first, and then added and subtracted
The multiplication rule of fractions: use the product of molecules as molecules and the product of denominators as denominators
Division of fractions: dividing by a number is equal to multiplying by the reciprocal of the number
2、 Unit conversion
(1) 1 km = 1 km, 1 km = 1000 m, 1 m = 10 decimeter, 1 decimeter = 10 cm, 1 cm = 10 mm
(2) 1 square meter = 100 square decimeter 1 square decimeter = 100 square centimeter 1 square centimeter = 100 square millimeter
(3) 1 cubic meter = 1000 cubic decimeter 1 cubic decimeter = 1000 cubic centimeter 1 cubic centimeter = 1000 cubic millimeter
(4) 1t = 1000kg 1kg = 1000g = 1kg = 2kg
(5) 1 hectare = 10000 square meters, 1 mu = 666.666 square meters
(6) 1 liter = 1 cubic decimeter = 1000 ml 1 ml = 1 cubic centimeter
(7) 1 yuan = 10 Jiao 1 jiao = 10 Fen 1 yuan = 100 Fen
(8) The first century = 100 years, the first year = December, the big month (31 days) has: 1 / 3 / 5 / 7 / 8 / 10 / 12, the small month (30 days) has: 4 / 6 / 9 / 11
The average year is 28 days in February, leap year is 29 days in February, leap year is 365 days, leap year is 366 days, 1 day = 24 hours, 1 hour = 60 minutes
1 minute = 60 seconds 1 hour = 3600 seconds
3、 On the calculation formula of quantity relation
1. Number of copies × number of copies = total number of copies / number of copies = total number of copies / number of copies = number of copies
2. 1 times × times = several times △ 1 times = several times △ 1 times
3. Speed × time = distance △ speed = time distance △ time = speed
4. Unit price × quantity = total price / unit price = total quantity / quantity = unit price
5. Work efficiency × work time = total amount of work △ work efficiency = total amount of work time △ work time = work efficiency
6. Addend + addend = sum - one addend = another addend
7. Subtracted - subtracted = difference subtracted - difference = subtracted difference + subtracted = subtracted
8. Factor × factor = product △ one factor = another factor
9. Divisor / divisor = quotient divisor / quotient = divisor quotient × divisor = divisor
4、 Arithmetic
1. Additive commutative law: two numbers are added to exchange the position of addends, and the sum remains unchanged
2. The law of combination of addition: add three numbers, add the first two numbers first, or add the last two numbers first, and then the same as the third number
The sum of three numbers is constant
3. Commutative law of multiplication: when two numbers are multiplied, the position of commutative factor is unchanged
4. The law of combination of multiplication: when three numbers are multiplied, the first two numbers are multiplied, or the second two numbers are multiplied, and then the third number is multiplied, so that their product remains unchanged
5. Law of distribution by multiplication: multiplication of two numbers and the same number, two addends can be multiplied by the same number respectively, and then the two products can be added up, and the result remains unchanged. For example: (2 + 4) × 5 = 2 × 5 + 4 × 5
6. The nature of division: in division, the divisor and the divisor expand (or reduce) the same multiple at the same time, and the quotient remains unchanged. 0 divided by any number that is not 0 will get 0
7. Equation: the equation that the value on the left side of the equal sign is equal to the value on the right side of the equal sign is called the equation. Basic properties of the equation: if both sides of the equation multiply (or divide) the same number at the same time, the equation still holds
8. Equations: Equations with unknowns are called equations
9. Unary linear equation: the equation with an unknown number and the degree of the unknown number is once is called unary linear equation
Learn the example method and calculation of linear equation of one variable, that is, give the formula with χ and calculate
10. Fraction: the unit "1" is divided into several parts equally, which means such a part or fraction
11. The law of addition and subtraction of fractions: add and subtract fractions with the same denominator, only add and subtract molecules, and the denominator remains unchanged. Add and subtract fractions with different denominators, and then add and subtract
12. Comparison of fractions: compared with fractions with the same denominator, fractions with larger numerator are larger and fractions with smaller numerator are smaller. Compared with fractions with different denominators, fractions with the same denominator are divided first and then compared. If the numerator is the same, fractions with larger denominator are smaller
The numerator is the product of the numerator of a fraction and the integral, and the denominator remains unchanged
14. Fraction multiplied by fraction, using the product of multiplication of molecules as the molecule and the product of multiplication of denominators as the denominator
15. Dividing a fraction by an integer (except 0) is equal to multiplying the fraction by the reciprocal of the integer
True fraction: the fraction whose numerator is smaller than denominator is called true fraction
17. False fraction: the fraction whose numerator is larger than denominator or whose numerator and denominator are equal is called false fraction. False fraction is greater than or equal to 1
18. With fraction: it is called with fraction to write the false fraction in the form of integer and true fraction
19. Basic properties of fraction: the numerator and denominator of fraction multiply or divide by the same number (except 0), and the size of fraction remains unchanged
A number divided by a fraction is equal to the number multiplied by the reciprocal of the fraction
21. Number a divided by number B (except 0) is equal to the reciprocal of number a multiplied by number B
5、 Special issues
The formula of sum difference problem
(sum + difference) △ 2 = large number
(sum difference) △ 2 = decimal
The problem of sum times
Sum (multiple-1) = decimal
Decimals × multiples = large numbers
(or sum - decimal = large)
Differential multiple problem
Difference (multiple-1) = decimal
Decimals × multiples = large numbers
(or decimal + difference = large)
The problem of tree planting
1. The tree planting problem on non closed lines can be divided into the following three cases
(1) If trees are to be planted at both ends of an unclosed line, then:
Number of plants = number of segments + 1 = total length △ plant spacing-1
Total length = plant spacing × (number of plants - 1)
Plant spacing = total length (number of plants - 1)
(2) If trees are to be planted at one end of an unclosed line and not at the other end, then:
Number of plants = number of segments = total length △ plant spacing
Total length = plant spacing × number of plants
Plant spacing = total length △ number of plants
(3) If you do not plant trees at both ends of an unclosed line, then:
Number of plants = number of segments-1 = total length △ spacing-1
Total length = plant spacing × (number of plants + 1)
Plant spacing = total length (number of plants + 1)
2. The quantitative relationship of tree planting on closed lines is as follows
Number of plants = number of segments = total length △ plant spacing
Total length = plant spacing × number of plants
Plant spacing = total length △ number of plants
Profit and loss
(profit + loss) △ the difference between the two distributions = the number of shares participating in the distribution
(big profit - small profit) △ the difference between the two distributions = the number of shares participating in the distribution
(big loss - small loss) △ the difference between the two distributions = the number of shares participating in the distribution
Encounter problem
Encounter distance = speed and X encounter time
Encounter time = encounter distance △ speed and
Speed sum = encounter distance △ encounter time
Follow up questions
Pursuit distance = speed difference × pursuit time
Pursuit time = pursuit distance △ speed difference
Speed difference = pursuit distance △ pursuit time
Flow problem
(1) General formula:
Downstream velocity = hydrostatic velocity + water velocity
Countercurrent velocity = still water velocity - water velocity
Hydrostatic velocity = (downstream velocity + countercurrent velocity) △ 2
Water flow velocity = (downstream velocity countercurrent velocity) △ 2
(2) The formula of two ships sailing in opposite directions:
Ship a's downstream speed + ship B's upstream speed = ship a's still water speed + ship B's still water speed
(3) The formula of two ships sailing in the same direction:
Still water velocity of fore (AFT) ship - still water velocity of fore (AFT) ship = speed of reducing (increasing) distance between two ships
Concentration problem
Weight of solute + weight of solvent = weight of solution
Weight of solute / weight of solution × 100% = concentration
Weight of solution × concentration = weight of solute
Weight of solute △ concentration = weight of solution
Profit and discount
Profit = selling price cost
Profit margin = profit / cost × 100% = (selling price / cost-1) × 100%
Up and down amount = principal ×