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Make up unit Zhang Wei's height is 16.6_____ 7.5km=______ m； 5.85mm=_____ m； 0.068m=_______ nm； 16.4m=______ um； 1.8h=____ min； 45min=_____ h
m,7500,0.00585,68000000,16400000,108,0.75
1、_______ It shows that sunlight is a mixture of seven colors_______ Yes, the spacecraft works with photocells______ Can be transformed into_______ Yes. "Everything is born by the sun" shows that the photosynthesis of plants can______ Can be transformed into_______ can
Astigmatic light energy light energy electric energy light energy chemical energy
At the turning of an expressway, the curve radius is r = 100m, and the dynamic friction coefficient between the vehicle tire and the road surface is u = 0.23. When the vehicle runs on this section of the road at the speed of u = 15m / s, if the vehicle does not slide left and right, what is the inclination angle Δ of the road facing the center of the circle? (g) take 10m / s2
The component of gravity is equal to the centripetal force. First find the centripetal force Tan, and the centripetal force is equal to the inclination angle
Come and help me with my physics problem Resistors R1 are 5V, 0.25W, R2 are 2V, 0.25W... Connect them in series and connect them to the circuit. In order to ensure that these two resistors do not overload, how much voltage is added to both ends of them? There should be a detailed process
Here's the easiest way:
P=UI
Then the rated current of R1 is 0.25w/5v = 0.05A
The rated current of R2 is 0.25w/2v ＝ 0.125A
Obviously, the maximum current used in series cannot exceed the rated current of R1
Therefore, the maximum voltage is 0.05A * (R1 + R2) = 0.05A * (U1 ^ 2 / P1 + U2 ^ 2 / P2)
=0.05A*(100Ω+16Ω)=5.8V
It is reported that China's first maglev train experimental line has entered the experimental operation stage in Shanghai. It uses the interaction between two magnetic poles with the same name______ The principle makes the train suspended on the track up to 10cm, thus reducing friction and greatly improving the running speed of the train. Its average speed is about 4 times that of ordinary trains, which has the advantages of energy saving and time saving. The k308 train from Xiamen to Beijing needs to run for about 34 hours. If it is changed into a maglev train, it needs to run for about 30 hours______ You can get to Beijing from Xiamen in an hour
Maglev train works on the principle of mutual exclusion of magnetic poles with the same name;
Set the distance from Xiamen to Beijing as s; If it is changed into a maglev train, the operation time is about t = s
V=S
4V normal = 1
four × 34h=8.5h．
So the answer is: rejection; 8.5．
Master, come and help us solve a physics problem of pulley block As shown in Figure 7-12, a pulley block is used to pull out a car trapped in the mud. If a person pulls a car with a mass of 8x103kg at a uniform speed along the horizontal direction with a tensile force F of 1600n, if the resistance received by the car is 0.05 times the weight of the car, the car advances 5 m in 10 minutes. According to the conditions given in the question, please calculate three physical quantities related to the question. (g takes 10N / kg)
Vehicle gravity g = 8x103kg x10n / kg = 8x104n
Resistance f = 8x104n x 0.05 = 4000N
Tensile force F = 4000nx1 / 3 = 1333n
Speed v = 5m X1 / 10 = 0.5m/s
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- 12. As shown in the figure, use the spring scale to horizontally pull the object block weighing 10N, place the object block on the horizontal desktop, and gradually increase the tension. When the indication of the spring scale is 2.2n, the object block begins to slide. In order to maintain the uniform movement of the object block, the later tension is only 2.0N. Then the maximum static friction between the object block and the desktop is______ N. The dynamic friction coefficient between the block and the table is __
- 13. The distance between the slide and the lens position changes between 15 ~ 30cm. In order to get an enlarged image on the screen, which of the following focal lengths should be selected () A. focal length 15cm B. focal length 30cm the correct answer to this question is a, but to get an enlarged image, the object distance should be between F < U < 2F. The farther the lens is, the larger the image will be. Why not choose B and a? Be clear,
- 14. When stone a falls freely from the top of the tower from static S1, stone B falls freely from static S2 from the top of the tower. If the two stones fall to the ground at the same time, the tower height is: () a S1 + S2 B (S1 + S2) ²/ 4S1 C S1 ²/ 4（S1+S2) D (S1+S2) ²/ S1-S2
- 15. As shown in Figure 1, the current in a long straight wire changes according to the sinusoidal law as shown in Figure 2. It is specified that the current is positive from left to right. There is an open metal frame below the straight wire. Therefore, compared with point B, the moment when the potential at point a is the highest is () A. T1 time B. T2 time C. T3 time D. T4 time
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