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Anonymous users2024-02-06Chapter 1: Force and Machinery.
How to recognize power.
1. Generation of force: Force is the action of an object on an object.
2. The effect of force: deform the object;
Change the state and orientation of the object.
3. The action of force is mutual.
4. The three elements of force: size; Direction; Point of effect.
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Anonymous users2024-02-05Question 2: As shown below.
Question 3: Since light propagates in a straight line in the same homogeneous medium, blocking the light from shining on the opaque object, and the opaque object blocks the propagation of light, so a shadow is formed where the light cannot shine.
Question 4: Examples of light flame propagation in a straight line: shadow formation, solar eclipse, lunar eclipse.
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Anonymous users2024-02-042. The frog at the bottom of the well) drawing: the left eye of the frog to the left and right sides of the well, and the right eye of the frog to the left and right sides of the well. 3 Explain the shadow) Light travels in a straight line, encountering some opaque obstacles, the light cannot penetrate, so there is no light in the part blocked by the object, thus forming a shadow.
4 (Examples of light propagating in a straight line) Shadows, image of small holes, sunlight in the shade of trees...Teaching materials may differ.
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Anonymous users2024-02-03Your current book is a new one, and it's different from my original one, so I'm sorry for you to post the title.
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Anonymous users2024-02-021. Because the wall of the well blocks the viewing angle of the glasses, hindering the straight line propagation of light. 2. Straight line propagation of light 3. Queue up Yes, it looks like the laser is collimated.
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Anonymous users2024-02-011. The distance between the two objects A and B always remains the same, and the object A moves to the east, so if the object B moves in the direction of object B as a reference, then object A is.
Kilometer-hour = meter-second 10-meter-second = kilometer-hour.
3, a car drives at a constant speed of 10 meters seconds at the first 20 meters of motorcycle, when the car travels for 5 seconds, the motorcycle goes to catch up with the car at a speed of 15 meters and seconds, when the motorcycle catches up with the car time is seconds, and the distance between catching up with the car and the starting point of the car is.
4. The average speed of Wang Xin's normal walking is meters and seconds, and it takes 20 minutes to walk from home to school, so the distance he has to walk to school is about meters, and if he rides a bicycle to school at a speed of meters and seconds, he must leave the house a few minutes early so that he will not be late.
5. The speed of uniform linear motion is unchanged, and the speed of a train is 20 meters and seconds, which is equivalent to kilometers and hours. It is pronounced .
6. A student walks from home to school and spends 15 minutes at school, of which the first 1 3 time walks 500 meters, then 1 3 time walks 300 meters, and the last 1 3 time walks 600 meters. Then the average speed of the student in the first 10 minutes is meters, the average speed in the second 10 minutes, and the average speed from home to school is meters.
Go to the Internet to search for them, a lot of translations!
1.(1) Reflected light; Transmit light.
2) The position of the image and the size of the object. >>>More
1.The eardrum of the human ear is a thin, elastic membrane like the membrane of the drum, and when sound waves pass through the ear canal to the eardrum, the eardrum vibrates and transmits this (vibration) to the cochlea >>>More
If both balls of equal volume A and B float on the water, then the buoyancy received by the two balls of A and B is equal to the gravitational force received by A and B respectively, but A and B are only equal in volume and do not know the density, so the amount of buoyancy they receive cannot be determined, so D is chosen. >>>More
Replace * to the 2nd power.
Common; （a+b）*=a*+2ab*+b*：（a-b）*=a*-2ab*+b* >>>More