Connect a small light bulb marked with "3V, 0.6W" to a 4.5V power supply. In order to make the small light bulb shine normally, it is necessary to____ Join one_____ O (Ohm) resistance

Connect a small light bulb marked with "3V, 0.6W" to a 4.5V power supply. In order to make the small light bulb shine normally, it is necessary to____ Join one_____ O (Ohm) resistance

Connect a small light bulb marked with "3V, 0.6W" to a 4.5V power supply. In order to make the small light bulb shine normally, it is necessary to__ Series connection__ Join one___ 7.5__ (Ohm) resistance

The projection of one vector on another
How to calculate the projection length of vector a on vector B? Is it a * B / | B?

Yes

I'm hungry for the physics exam today

Buoyancy f floating (n) f floating = g object - G view g view: gravity of object in liquid
Gravity g (n) g = mg m: mass
The direction of resultant force F (n) is the same: F = F1 + F2
Buoyancy f floating (n) f floating = g object
This formula is only applicable to floating or floating objects
Buoyancy f floating (n) f floating = g row = m row g = ρ liquid GV row
Row G: the gravity that displaces the liquid
M row: the mass of liquid in row
ρ liquid: density of liquid
V-row: volume of liquid discharged (i.e. volume immersed in liquid)
Balance condition of lever f1l1 = f2l2 F1: power L1: power arm
F2: resistance L2: resistance arm
Pressure P = f / S
Gravity g: the force exerted on an object due to the attraction of the earth
Relationship between gravity and mass: g = mg m = g / g
Newton's first law is also known as the law of inertia. Its content is: when all objects are not affected by external forces, they always maintain a state of static or uniform linear motion. Inertia: objects have the property of maintaining the original state of static or uniform linear motion, which is called inertia
The formula of liquid internal pressure: P = ρ GH
Heat Q (J) q = cm △ t
c: Specific heat capacity of matter
m: Quality
Δ T: change value of temperature
Fuel emission
Q (J) q = MQ M: mass
q: Calorific value
Fixed pulley f = g
S = H F: the tension on the free end of the rope
G object: the gravity of an object
S: The distance that the free end of the rope moves
h: The distance an object rises
Speed V (M / s) v = s / T; s: distance, t: time
Moving pulley f = (g object + G wheel) / 2
S = 2 h g object: the gravity of the object
Wheel G: gravity of moving pulley
Pulley block f = (g object + G wheel)
S = N H N: the number of segments of the rope passing through the movable pulley
Mechanical work w (J) w = FS
F: Strength
s: The distance moved in the direction of the force
Useful work W has = g matter H
Total work w total w total = FS when the pulley block is placed vertically
Mechanical efficiency η = Wye / wtotal × 100%

A wooden block with a mass of M is resting on a light spring. Now, the vertical downward force F is used to slowly press down the wooden block. When it reaches a position, it suddenly lets go and the wooden block makes a simple harmonic motion
Q: is force f a constant force?
Because of the simple harmonic motion of the block, is the position of reduction amplitude?

1. Force F is not a constant force, f increases continuously
Slow pressing is to ensure the force balance of small blocks
F = k * x (Hooke's law, where x is the moving distance relative to the initial position). Obviously, as the pressure distance increases, that is, x increases, f increases
2. It's amplitude

The AC cycle is 0.02 seconds and the frequency is 50 Hz
How many cycles per second? How many times does the direction change?

50 cycles per second, direction change 100 times
Change direction twice for a cycle

Can a balance be used in space
Can the balance work properly in space without neutrality

The balance measures the mass of an object, not gravity, which is the essence
On the earth, the most obvious manifestation of mass is gravity, so we have the impression that the balance can only be placed on a plane to see which tray is heavier under the action of gravity. But it does not mean that the balance is "something relying on gravity"!
In space, as long as there are some necessary devices, the balance can still be used. For example, a large rotating wheel, or a linear accelerator. In short, f = mg is not the only choice. It can be replaced by F = mw2r, f = ma, or even others. This is like using an elevator to simulate the overweight situation, and then doing experiments in it. The effect is the same as the actual gravity field
The simulated overweight environment does not violate the condition of "losing gravity". The definition of gravity: "the gravity of an object rotating with the earth is called the gravity of the object." it has strong conditionality. As long as it is not affected by the earth, it is not gravity

The area of a square is a function of its perimeter. Why?
We need to know why

If the perimeter is x, then the side length is x / 4 and the area is y = (x / 4) ^ 2 = x ^ 2 / 16
x> 0, which is a quadratic function

According to f = ma, the force should have acceleration, but if
If the constant force and friction are offset, then we will move in a straight line at a constant speed. What's the answer downstairs? Then it must be a constant acceleration. If we change the object into a particle. Considering the friction is really my own idea. I just want to make sure what motion is possible. Constant force must be uniform acceleration? Can't it be uniform?

It depends on how the constant force works, and it is not clear whether it is affected or only affected. If it is, there may be other possible forces. 1. When it is only affected by a constant force, if the constant force F presses down the original static object vertically, the object will remain static; if the oblique upward (downward) constant force

Four mixed operations with 4 digits in Grade 6 of primary school (only including integers)
Do not carry *, /

1) 7034044÷(6799-3771)×3388= 2) 806+3504-5366515÷1855=
3) 6408-2595+1828×1514= 4) 4003449÷(7056-3643)×2850=
5) 1435+1431689÷901-1023= 6) (1710223-223)÷1520-828=
7) 2912+(3423-543)×2362= 8) (753+616)×341-272767=
9) 8917-(1624+113778÷27)= 10) 897×(700917-267)÷865=
11) 1559-(59+1036)÷66294= 12) (6701574+2082)÷(4783-1891)=
13) (2215161+689)÷(4409-3499)= 14) 339+( 3716330-830 )÷1500=
15) (853+781)×3029892÷1843= 16) 473077÷(3577-2094)×838=
17) 1304+(269005-1597)÷1857= 18) 4802+1077090÷1338-1604=
19) 1686916-1686417÷(402050÷550)= 20) 2497+(2743-255)×1029=
21) (2043+913)×850-1870673= 22) 952232-543006÷933×1635=
23) 1926211÷(2515-1334)×293= 24) (994772-722)÷2350-301=
25) 62513-61674÷(65208÷1716)= 26) 1577-810+497×237=
27) 1061+767916÷1028-641= 28) 1257×(755451-909)÷1602=
29) 628044÷(2257-1461)×301= 30) 2392×( 1281341-2477 )÷321=
31) 796390÷1085×1233-538472= 32) 22238898÷4906×4341-2590302=
33) (1970-845171÷2753)×574= 34) 182+464-271622÷806=
35) 4968579÷2877×2493-1273981= 36) 357994÷(822-260)×690=
37) 655270÷(1016-165)×552= 38) (9689874-194)÷3388-2029=
39) (400+161)×673-118257= 40) (1121+1355)×2770871÷1907=
41) 4679-3562+1498×932= 42) 710-(626+1252)÷1013070=
43) 387+(64591-736)÷129= 44) (11216801+151)÷(7637-3883)=
45) 3797+(8016539-2339)÷2280= 46) 7176-3083+846×2370=
47) 335-(1793+731)÷1191378= 48) 3361526-3357585÷(314127÷167)=
49) 1358+8840-14984541÷3861= 50) 765+1007×1219-67=

The dynamic friction factor u = 0.5 when the mass m = 2kg is placed on a horizontal plane
The object with mass of M = 2kg is placed on the horizontal plane, and the dynamic friction factor between them is u = 0.5. Now the force of F = 20n is applied to the object, and the direction is inclined upward at an angle of 37 degrees to the horizontal (g = 10m / S ^ 2)
(1) What is the acceleration of motion?
(2) What is the displacement of the object passing through 5s under the action of force F?
(3) If the force F is removed after 5S, how far can the object slide after removing f?

1. Decompose the f-focus, the horizontal force F1 = f * cos37 = 16N, and the vertical force F2 = f * sin37 = 12n
f=u(mg-F2)=4N a=(F1-f)/m=6m/s2
2 s=1/2at2=75m
3 V = at = 30m / s the acceleration after removing f a = f = UMG = 10m / S2 s = V2 / 2A = 45m