"Measuring Average Speed" Mechanical Movement PPT Courseware 6

"Measuring Average Speed" Mechanical Movement PPT Courseware 6

Learn from demonstrations and improve plans

Experimental equipment: trolley, long wooden board, spacer blocks, iron clamps, small iron bookends, and pencils.

①How to place and adjust the incline (track)?

②How to determine the starting point and end point of the movement? How to get the distance?

③How to record time?

④How to get the average speed?

Group discussion and presentation of results

① Raise one end and tilt it slightly so that the car can move actively but not too fast.

② At the release point of the trolley, mark the front end of the trolley as the starting point; stick a metal piece on the lower end of the slope as the end point, and use a scale to measure the distance from the starting point to the end point, which is the distance s.

③When releasing the car, use the stop watch to start timing. When the car hits the metal piece, stop the timing and get the time t.

④Calculate the speed from v=s/t.

Teachers and students summarize and improve the plan

① Are there any problems with the operation just now?

a. The division of labor and coordination (starter, operator, timekeeper, recordkeeper) must be done in advance.

b. Each set of data should be measured several times and the average value should be taken.

②The experiment requires two results: moving to the bottom and moving to the midpoint. What should I do?

The experiment is divided into two major steps: after the metal piece is stuck at the bottom and measured, the metal piece is stuck in the middle and measured. Each measurement can be measured more than three times.

Experiment Summary Problem Discussion

Question ①: Why are the two speeds v1 and v2 obtained by each group different? Are the two related twice?

The car goes faster and faster, and the second half is faster, so the whole speed is greater than the speed in the first half, but it is not a double relationship (v2

Question ②: Why are the measured values ​​different between the groups? Is it due to errors?

It's not the reason for the error. First, the inclination angle of the slope is different, so the speed is different; second, the distance is not consistent, so the speed obtained is different from each other.

Question ③: Which aspects does the experimental error mainly come from?

The first is limited by the accuracy of the tool; the second is the response speed and reading error of the measurer; and the third is the error caused by uneven smoothness of the device.

Question ④: To reduce the error, what should we pay attention to?

a. When installing the device, the inclination angle of the slope should be smaller, but not too small. If it is too small, the trolley will not move. If it is larger, the trolley will be too fast and the timing will be inaccurate. It is better if the distance between the starting and ending points is appropriately larger.

b. When measuring the same set of data, ensure that the starting and ending points are the same.

c. When measuring time, the release of the car and the start of timing should be synchronized as much as possible.

d. The scale and stopwatch readings must be standardized and accurate.

Class summary

1. Measure the "average speed of the car moving on the slope"

①Principles and equipment;

②Method steps;

③Error analysis and points of attention.

2. Improvement and expansion of experiments

① Photoelectric timing, air cushion guide rail;

②Ultrasonic ranging, computer measurement, display speed.

3. Example applications and extensions

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