2. temperature t

3. speed v

4. Density p

5. Force (gravity) f

6. pressure p

7. Work w

8. power supply p

1. Force (f): Force is the action of objects on objects, and the action of forces between objects is always mutual. Unit of force: Newton (n).

Second, the three elements of force: the size, direction and action point of force are called the three elements of force. The diagram of force should be proportional; Schematic diagram of forces, not to scale.

3. Gravity G: the force exerted on an object due to the attraction of the earth. Direction: vertical downward. The relationship between gravity and mass: G=mg m=G/g, g=9.8 N/kg. Reading method: 9.8 N/kg, which means that the gravity of an object with a mass of 1 kg on the earth is 9.8 N. ..

Extended data:

Optics:

1. Linear propagation of light: Light propagates linearly in the same homogeneous medium. Aperture imaging, shadow and spot are all linear propagation phenomena of light. The maximum speed of light in vacuum is 3x108m/s = 3x105km/s.

Second, the law of light reflection: one side, two sides and three dimensions. The angle between the incident light and the normal is the incident angle. The angle between the reflected light and the normal is the reflection angle.

1, plane mirror imaging characteristics: virtual image, equal size, equal distance, mirror symmetry. The reflection of objects in water is the reflection of virtual images and light.

2. In the plane mirror imaging experiment, replacing the plane mirror with glass can easily find the position of the image and compare the size relationship between the image and the object.

Third, the phenomenon and law of light refraction: seeing the virtual images of chopsticks and fish in water is the phenomenon of light refraction. Convex lens has the function of converging light, while concave lens has the function of diverging light. The law of refraction of light: one side, two sides, three sides, big four empty.

Fourth, the law of convex lens imaging: when U=f, the real image with inverted size when U=2f and V=2f is not imaged.

1, u & gt2f f<v & lt2f reverse zoom, camera.

2, f<u & lt2f v & gt2f inverted amplification, slide projector.

3. u< magnifier

5. Convex lens imaging experiment: Put the candle, convex lens and light screen on the optical experimental platform in turn, so that the centers of the candle flame, convex lens and light screen are at the same height.

Baidu encyclopedia-junior high school physics