All the formulas of physics work in junior high school are not w = f × s It's not the total

All the formulas of physics work in junior high school are not w = f × s It's not the total

w=pt

The formula of physical work and power in junior high school

Merit:
W = fs (definition of work)
W-work, f-force, s-distance
Work is the product of the distance s that a body moves under the action of force F
Power:
P = w / T (power definition)
To show how fast work is done, divide work by time
Power refers to how much work an object does in a unit time
From P = w / T = f * s / T = FV, this is a mathematical operation
It doesn't have much physical meaning and is usually used for calculation
Mechanical efficiency
η = w useful / W Total (definition of mechanical efficiency)
This physical quantity is to express the usefulness of a machine
That is to measure the difference between the "cost" and "benefit" of machinery
Attachment: units and symbols of physical quantities
Work-w-joule-j
Power-p-watt-w
(mechanical efficiency is usually expressed as percentage, without sign)

Why is the formula of kinetic energy EK = 1 / 2mV ^ 2
Such as the title

Consider using constant force F to stop an object with m and V
Acceleration f / M
The moving distance is v ^ 2 / (2f / M)
So the negative work of the force is 1 / 2mV ^ 2 / f * f = 1 / 2mV ^ 2
So 1 / 2mV ^ 2 is the kinetic energy of the object
Although this is derived from the special case of constant force, it can be proved that the same is true for the general case

If the generatrix length of a cone is three times the radius of its bottom circle, then the center angle of its side expanded view is______ Degree

2 π r = n π· 3r180, the solution is n = 120 ° and the center angle of the side view is 120 degrees

Solve the following equation, and check the second problem
5x+4=24
4x-12=48

(1)5x+4=24
5x=24-4
5x=20
x=20÷5
x=4
(2)4x-12=48
4x=48+12
4x=60
x=60÷4
x=15
Checking calculation: substitute x = 15 into equation 4x-12 = 48
4×15-12
=60-12
=48

Solution set of inequality | x2-10 | ≤ 3x

|x2-10|≤3x
If x2-10 ≥ 0 and x2-10 ≤ 3x, then √ 10 ≤ x ≤ 5
If x2-10 ≤ 0 and - x2 + 10 ≤ 3x, 2 ≤ x ≤ √ 10
SO 2 ≤ x ≤ 5

If the diameter of the small circle is equal to the radius of the big circle, the circumference of the big circle is () times that of the small circle, and the area of the small circle is several percent of that of the big circle

If the diameter of the small circle is equal to the radius of the big circle, the circumference of the big circle is (2) times that of the small circle, and the area of the small circle is 25% of that of the big circle
1÷（2x2）=25%

The sum of the four numbers of ABCD is 270. A is 10 more than B, 25 more than C, and 35 more than D. what are the four numbers?

B=A-10
C=A-25
D=A-35
A+B+C+D=A+（A-10）+（A-25）+（A-35）=270
4A-70=270
4A=340
A=85
B=85-10=75
C=85-25=60
D=85-35=50

The following polynomials are polynomials of several degrees, and the coefficients / degrees of each of them are given
-2x+1
Quadratic of x-xy + quadratic of Y
3X-4X+1
-mn-m+1

Number of items 2 times 1
Number of items 3 times 2
Number of items 2 times 1
Number of items 3 times 2 m once n once

How to find the radius of chord length and arch height
Do you know that arc length, chord length and arch height can not be calculated

It's not enough to know the chord length
You should know the degree of the central angle or the degree of the arc