What does the formula of sliding friction mean?

What does the formula of sliding friction mean?

Sliding friction = sliding friction coefficient * positive pressure

Calculation formula of sliding friction
What is the positive pressure of N in F = μ n?
For example, an object on a horizontal table is supported by gravity and a pull force at an angle of 30 ° to the horizontal plane. Is g balanced with the supporting force or is g balanced with the supporting force and the component force of the pull force in the vertical direction? Is n used to calculate the sliding friction force or is the component force of the supporting force and the pull force in the vertical direction?

N refers to the pressure on the plane. If there is no tension at 30 degree angle, then n is g, because g and supporting force are a pair of balanced forces! But if the tension at 30 degree angle is added, then n is g minus the difference of component forces in the vertical plane (g-sin30 ° f tension)! Then the sum of component forces in the vertical plane of G and N plus tension is a pair of balanced forces!

This paper defines a new operation, whose rule is a ★ B = a + B-1. According to this rule, the value of 2} (- 3) is

2+(-3)—1=—2

When 3V voltage is applied at both ends of a toy motor, the passing current is 0.3A, and the electric power of the motor is______ The resistance of the motor is______ (fill in "greater than", "equal to" or "less than") 10 Ω

(1) The electric power of the motor: P = UI = 3V × 0.3A = 0.9W; (2) ∵ the motor is a non pure resistance electrical appliance, part of the consumed electric energy is converted into mechanical energy, and part of it is converted into electric heating, ∵ the resistance of the motor should be less than 10 Ω, otherwise there will be no mechanical energy output

Calculate the values of 2,2 + 4,2 + 4 + 6,2 + 4 + 6 + 8 respectively

S1=2
S2=2＋4
S3=2＋4＋6
S4=2＋4＋6＋8
……
It can be found that the number of lines n is 2n more than that of line n-1
So:
Sn=2＋4＋6＋… ＋2n=n(n＋1).

Two resistors are connected in parallel, R1 = 5 ohm, R2 = 20 ohm, and the known trunk current is 0.5A. Calculate the voltage at both ends of the circuit and the current through the resistor
As the title says

U1=U2
I1*5=I2*20
I1+I2=0.5
I1=0.4A
I2=0.1A
U=I1R1
=0.4*5
=2V

In the parabola y2 = - 8x, the linear equation of the chord with (- 1,1) as the midpoint is ()
A. x-4y-3=0B. x+4y+3=0C. 4x+y-3=0D. 4x+y+3=0

The chord is not perpendicular to the x-axis, so let the point (- 1,1) be the parabola of the midpoint, and the two ends of the chord y2 = - 8x be a (x1, Y1) B (X2, Y2) to get yi2 = - 8X1, Y22 = - 8x2. Subtracting the two formulas to get (Y1 + Y2) (y1-y2) = - 8 (x1-x2) ∫ Y1 + y2 = 2 ∧ k = - 4 ∧ the linear equation is y + 1 = - 4 (x-1), that is 4x + y + 3 = 0, so choose: D

If a 4 ohm wire is separated into two wires and used in parallel, the resistance is
A. 4 euro B.3 Euro C.2 euro D.1 Euro

D

9 (3x-1) &# 178; = 64 to find the value of X (the process should be detailed)

9（3x-1）²=64
（3x-1）²=64 /9
（3x-1）=±√64 /9
（3x-1）=±8/3
3x=8/3+1 x=11/9
3x=-8/3+1 x=-5/9

How many hours can a 25 watt bulb shine normally at 2 kilowatt hours? How many hours can a 40 watt bulb shine normally at 1 degree? What's the process

The normal luminous time of 25 watt bulb with 2 kwh t = w / P = (2000 W · h) △ 25 = 80 H
1 degree = 1kW · H
The normal luminous time of a 40 watt bulb at 1 degree t = w / P = 1000 △ 40 = 25h