(2) Xiaoming's experiment is based on Archimedes' principle, F float =G row, and the hook code with small buoyancy uses large pulling force, so the hook code is immersed in water and salt water respectively, and the pulling force is measured by dynamometer, and the pulling force is water.
(2)① In the three experiments with serial numbers A, B and C, the volume of liquid displaced by the object is the same as that of submerged liquid, and the different factor is the mass of the object; As can be seen from the figure, the indicators of dynamometer are 3N, 3.5N and 4N respectively, while the weights of three cylindrical objects A, B and C are 4N, 4.5N and 5N respectively. According to the weighing method, the buoyancy is 1N, 1N and 1N respectively, and it can be concluded that the buoyancy is equal to the object.
In order to study the relationship between buoyancy and liquid density, according to the control variable method, it is necessary to keep the factors such as object volume, object mass and immersion depth unchanged, and the change amount is liquid density; Then the experiments that meet the requirements are: a, d and e.
(3) An example of the relationship between the magnitude of buoyancy and the depth of immersion of an object in a liquid is as follows:
When the salvaged object is lifted underwater, when the object is at different depths but does not reach the water surface, the applied pulling force remains unchanged; It shows that buoyancy has nothing to do with the depth of the object immersed in liquid.
(4) In the three experiments with serial number 1, 2 and 3, the volume of the object and the density of the liquid are the same, but the different factor is the volume of the liquid displaced by the object. From the data in the table, it can be concluded that buoyancy is related to the volume of liquid displaced by the object;
In the three experiments numbered 3, 4 and 5, the volume and density of the liquid displaced by the object are the same, and the different factor is the depth of the object. It can be concluded from the data in the table that buoyancy has nothing to do with the depth of the object;
So the answer is:
(1) Measure the same volume of water and brine with a measuring cylinder, pour them into two identical beakers respectively, and then put the two beakers on the left and right plates of the balance, with brine as the mass;
Dip the hook into water and salt water respectively, and measure the tensile force with dynamometer, and the tensile force is water.
(2) the quality of the object is irrelevant; a、d、e；
(3) When the salvaged object is lifted underwater, the depth of the object is different, but before reaching the water surface, the applied pulling force remains unchanged, indicating that the buoyancy has nothing to do with the depth of the object immersed in the liquid.
(4) Buoyancy has nothing to do with the depth of the object immersed in the liquid, but with the volume of the liquid displaced by the object.