First, the purpose of the experiment: the use of buoyancy to measure the quality of the object
Second, the experimental equipment
Plastic transparent cylinder Bar code Beverage bottle Object to be measured Balance (to verify the accuracy of the buoyancy scale)
Third, the experimental principle
This experiment is an innovative experiment that uses buoyancy to measure the mass of an object, using the learned buoyancy knowledge to make a buoyancy scale. First find an empty beverage bottle with a columnar body, cut off the bottom of the bottle, tighten the cap, attach a suitable mass of stone to the cap, and then invert it into the bucket as shown. When using, as long as the object to be tested is put into the bottle, the quality of the object to be measured can be read directly from the scale of the water surface.
Some notes on this instrument experiment
1, the role of hanging stones
As shown in the figure, when the buoyancy is equal to gravity, the buoyancy scale will float vertically in the water (if there is no stone, the center of gravity of the whole set will be higher than the point of buoyancy. Under the action of buoyancy and gravity, the buoyancy scale is easy to lick. It is difficult to float vertically in the water.)
2, the quality of the scale is uniform
Let the mass of the measured object be the radius of the cylindrical portion of the beverage bottle as r. After the object to be measured is placed in the buoyancy scale, the depth of the bottle intrusion increases by h, then: when the buoyancy scale floats again, it increases. Buoyancy is equal to the increased gravity: F float = G ie: ρ water g r2h = mg can be obtained: h = because ρ water, r is a fixed value, so h is proportional to m, so the scale of the buoyancy scale is uniform of. 3. When the object does not float in the bottle, first record the position of the water surface to the bottle and make a mark. (The position is zero tick position, because there is no object, the mass is zero.) Next, put the weight of 300g into it. In the bottle, the bottle is lowered, and when floating, record the position of the water surface to the bottle and mark it (this position corresponds to 300g, which is the 300g tick mark, which is also the maximum measurement value of the buoyancy scale), because the quality scale is uniform. , from 0 scale to 300g scale 100 equal parts, then each aliquot represents 3g, so put different quality objects, different positions indicate different quality, the quality can be scaled by buoyancy scale. So this buoyancy scale The range is 0-300g, and the division value is 3g.

Balance measurement result 166.4g
V. Self-evaluation of the test
Success: This test uses the knowledge of buoyancy to directly measure the mass of the object through self-made test instruments, with less consumables and simple structure.
Highly innovative and easy to operate.
Inadequacies: Because the physical quantity measured by the test instrument during the production process is large, and the index value is large due to other factors,
The error in the test results is large, and the accuracy of the measurement results is not high.

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