7th grade Science 1, Science 7th grade lower

I don't know if that's what you're asking:

The most common timekeeping tools used in laboratories are stops (mechanical and electronic), and the exact value of the electronic stops can reach the second. When the mechanical stop watch is reading, it is necessary to read out the minutes separately (small plate:; One revolution is 15 minutes) and seconds (**:

One rotation is 30 seconds) and add them together. It has an accurate value of seconds.

Application: A stopwatch is a commonly used instrument for measuring time intervals. It is timed by controlling the rotation of the hands by using the isochronism of the pendulum.

On its front is a large dial with subdials above it. The second hand rotates along the major dial, and the minute hand rotates along the subdial. The sum of the time indicated by the minute and second hands is the measured time interval.

Directly above the watch there is a watch handle, and there is a button on it. Turn the button and wind it up, this is the power for the stopwatch to move. Press the button with your thumb and the stopwatch starts the timer; Press the button again, the stopwatch stops moving and takes a reading; Press it again and the stopwatch returns to zero, ready for the next timer.

In order to solve this problem, some stopwatches are equipped with a button on the left side of the watch handle, and when the watch moves, push this button up, and the watch stops; Push down to continue accumulating timers. ）

Resources.

Small handicap: 15 minutes for one revolution **: 30 seconds for one revolution and add them together.

A gymnast with a height of one meter stands 3 meters in front of a flat mirror, and his image in the mirror is 3 meters away from the mirror, forming an upright virtual image, like a tall meter.

At this time, the distance between the athlete and his statue is 3 meters.

: White light pollution White light pollution is a kind of light pollution, which mainly refers to the light pollution caused by the reflected light of the glass curtain wall, glazed brick wall, polished marble and various paints and other decorations of buildings in the city during the day. It can be said to be specular reflection, that is, the reflective surface of the object is smooth, and the light rays are reflected in parallel, such as mirrors, water surfaces, etc.

2.An upside-down magnified reality.

1) Ask a question: This creature is a mammal.

2) Establish hypotheses:

A: This creature is probably a mammal.

B: This creature is probably a fish.

C: This creature is probably an amphibian.

3) Collect data: There are organs such as the spine, lungs, heart, stomach, liver, intestines, etc., which are similar to those of humans. Also pregnant with deceased hatchlings.

4) Compare the factual basis and test the hypothesis: hypothesis A and B are negative.

5) Conclusion: This creature is a mammal.

1) Cover family manuscript 3500 km = 3,500,000 m = 35,000,000 dm = 350,000,000 cm = 3,500,000,000 mm = 3,500,000,000,000,000 μm = 3,500,000,000,000,000 nm.

34600000 mm = 3460000 cm = 346000 decimeters = 346000 meters.

4,500,000 nm = 4,500 microns = mm = cm = panicle return = m.

8m=8m；Wuxiao 12cm=; 268dm=； 6930000m=6930km

2) (3) What about units... The unit has not been replaced.

Take (car) as a reference.

Therefore, the trees and houses outside the window move relative to the height of the car.

9. Elevator room.

10. Rolling car.

11. Self.

12. Motion, motion, stationary, stationary.

15. The train is equal to the west of the first car and the west is the same as the direction of the first car to the east.

I use oneself or a car as a reference.