Grade 8 (Grade 2) Physics Reference Answers and Grading Opinions

1. Can you choose the correct answer? (***32 points, 1-8 each question has only one correct option, and each small question has 3 points. Put the serial number of the correct option in brackets; 9. 10 The topic is multiple choice, and each question has two or more correct options. 4 points for each small question, 2 points for choosing the right one but not all; Don't choose, choose the wrong 0 points)

1.B 2。 D 3。 C 4 explosive D 5。 A six. C 7。 An eight. D 9。 Automatic call distributor 10. BCD

Can you fill in the blanks with what you have learned? (*** 18 points, each space 1 point)

11.mdm12.450 or 4.5×10215013. Vibrating vacuum 14. Iron pipe air.

15. Linear propagation reflection virtual image 16. 4 4 17. Circle shortening 18. 30 reversible 19. Water or liquid.

Can you draw and answer the following questions correctly? (** 16, 4 points for each small question)

20. Drawing measuring cup: The upper half and the lower half are very small (1), with units and numbers (1), divided into four squares (1), with the upper half dense and the lower half sparse (1).

2 1. Normal, plane mirror, reflection angle and incident angle are equal, and the reflected light is 1 point.

22. Answer: Because people's hearing range is 20 Hz-20 Hz-20,000 Hz, the sound wave emitted by flies is 147Hz-200Hz, which is within people's hearing range, so people can hear it. The sound waves emitted by butterflies are at 5-6 Hz, which belongs to infrasound waves and people can't hear them.

23. the side of a tends to be thinner. B tick marks are on the back of the ruler. C scale is transparent (other reasonable answers are also acceptable).

4. Can you complete the following inquiry? (* * Among them, 26 questions, 24 questions and 26 questions scored 6 points, 25 questions and 27 questions scored 7 points)

24. Add cotton thread and straighten it. With proper auxiliary equipment, the answer is reasonable. )

25.( 1) dark; candle

(2) the same (or equal); Vertical; (to) equal to ...

(3)B(2 points)

26.( 1) high information (2) slow and fast vibration frequency

27.( 1) 1, 2,5 (3 points) When the shooting elevation is the same, the faster the shooting speed, the farther the shot will be (3 points).

(2) 45 ( 1)

5. Can you complete the following calculations?

28.( 1) can't feel at the same time. The speed of sound in air is much less than the speed of light, while color (light) propagates in air at the speed of light.

(2) δ t = 14.7s (no formula is needed)

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