Convex lens imaging, drawing: ① 0 ＜ u ＜ F, ② u = f, ③ f ＜ u ＜ 2F, ④ u = 2F, ⑤ u ＞ 2F, ⑥ 0 ＜ u ＜ F, ⑦ u = 3fu = 5F, f = 2cm

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• 1. Image appearance when u ＜ F, u ＞ 2F, u = f, f ＜ u ＜ 2F, u = 2F
• 2. Objects near the earth's surface must be affected by gravity, right?
• 3. The gravity of an object acts on its center of gravity. Is that right? Why
• 4. If an object is only affected by gravity, then A. It's possible to do curvilinear motion B. It can only move in a straight line at a constant speed C. It's impossible to change speed D. May remain stationary
• 5. Clay tile workers usually make it out of a small stone______ To check whether the walls are in good condition______ This is based on__________________________ It's made on the principle of
• 6. Which of the following experiments can be performed in an orbiting space station A. measure the density of the meteorite with a balance; B. observe the onion slices with a microscope; C. measure the temperature inside the chamber with a thermometer D the gravity of the object on the side of the spring dynamometer e the grip strength of the astronaut with the spring dynamometer
• 7. How do volume units be expressed in letters
• 8. What do 26 English letters look like? OK, I'll add 100 points
• 9. Letter symbols corresponding to chemical electrical instruments
• 10. The chemical quantity represented by each letter in chemistry Just as M is the mass and N is the quantity of matter Please do it in 26 letter order,
• 11. For the formula 1 / F = / F1 + 1 / F2 (F2 ≠ 2f), if f and F2 are known, the deformation result of the formula is
• 12. Letters and physical quantities What letter stands for what physical quantity? Where is all I want all of them. I don't want to introduce them. Just give the letters
• 13. The traffic police on duty on the Jingchang Expressway stopped a speeding car. After saluting the driver, the traffic police said, "your speed exceeds the limit of 120 km / h". Before the traffic police finished, a child in the car said, "we only drove for a few minutes, and we didn't have to wait If you are the traffic policeman, how can you explain to the children?
• 14. Physics of grade two (about force) The lovely Fuwa is having a sports match. The following is the statement about these scenes ..（ ） A when swimming, the force of the hand on the water keeps Beibei moving forward When B Beibei and Nini rowed, the rowing boat received a forward force, which had no force object When playing volleyball, Nini changed the shape of volleyball and the movement state of volleyball When playing football, the foot gives the ball a kick, and then the ball gives the foot a kick What? Why? Why is c good?
• 15. It is often used in science to show force directly
• 16. The unit of force is, abbreviated as, symbol
• 17. In equilateral triangle circuit, corresponding to three resistors, known as U1 = U2 = U3 = 380V, R1 = R2 = R3 = 48 ohm, calculate I1, I2, I3
• 18. Two resistors R1 and R2 are connected in parallel in the circuit. If the current I1: I2 passing through the resistor R1 and R2 is 4:3, the voltage ratio at both ends of the resistor R1 and R2 is () A.4:9 B：1:1 C.3:2 D.2:3
• 19. After resistor R1 and R2 are connected in parallel, they are connected to the power supply with voltage u, and the main circuit current is I. The current passing through R1 and R2 is I1 and I2 respectively. It is tried to prove that I1 = [R2 / (R1 + R2) Try to prove that I1 = [R2 / (R1 + R2)] I That is to say, I1 is equal to R2 divided by the sum of R1 and R2, and then multiplied by I}
• 20. The power supply voltage is 6V, the resistance R1 = 5 ohm, and the maximum resistance of rheostat R2 is 10 ohm Find out the change range of voltmeter and ammeter