CN212514117U - Density balance for middle school students - Google Patents

Density balance for middle school students Download PDF

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CN212514117U
CN212514117U CN202021127340.8U CN202021127340U CN212514117U CN 212514117 U CN212514117 U CN 212514117U CN 202021127340 U CN202021127340 U CN 202021127340U CN 212514117 U CN212514117 U CN 212514117U
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water
density
balance
middle school
determinand
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王振学
王彦博
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Abstract

The utility model relates to an experimental apparatus of ability direct measurement solid density, the left end hangs the determinand, the right-hand member hangs the water of arranging when the determinand submergence completely, it is unchangeable to keep left end length, confirm to be 1 unit length, place the determinand on the thing net of carrying of aquatic, the measurement process does not take out from the aquatic, the water partly inflow drainage container that will arrange, the water quality of arranging when total quality equals the determinand submergence completely, and hang in the right-hand member, direct adjustment is balanced the back reading can obtain the solid density that awaits measuring. The object measured by the experimental instrument is a solid which does not react with water and has density higher than that of water. The density balance for middle school students has simple structure, is convenient to assemble and is more beneficial to operation. The experimental instrument is beneficial to the middle school students to integrate physical and mechanical knowledge in the junior middle schools, and can be used for creating thinking training and improving practical ability.

Description

Density balance for middle school students
Technical Field
The utility model relates to a middle school student's density balance is a measuring instrument that can direct measurement solid density, belongs to middle school physics experimental apparatus field.
Background
The utility model discloses accomplish junior middle school's mechanics course at the student after, for taking exercise student's innovation thinking ability, the laboratory glassware of practical problem is solved to a comprehensive utilization knowledge of design. It uses the balance principle, lever principle, Archimedes' law and other physical knowledge and mathematical operation simplification in middle school physics to implement the ingenious thinking of solid density and lever length correlationAnd (5) dimension operation process. The concept of the density balance is proposed by the inventor in 1999 that students are organized to participate in the innovation competition, and then the principle, the structure and the thinking process of the density balance are explained in 2004 No. 9 of physical teaching reference of middle school, the core content of which is as follows: the solid density measurement in middle school physics needs three steps: measuring mass M by a mass balance, (II) measuring volume V by a drainage method, and (III) calculating rho-M/V. The density balance ingeniously integrates the processes, the principle of the density balance is shown in figure 1, AB is a beam of the density balance, O is a balance fulcrum, the left end is used for placing the substance to be measured, the mass is M, the right end is used for placing the water drained when the substance to be measured is completely immersed, the mass is M, the volume is V, the OA length is kept unchanged and is determined to be 1 unit length, the position for draining the water is moved, the density balance is balanced, and Mg & OA & Mg & OB & gt is obtained according to the lever principle. (Mg is the weight of the product, Mg is the weight of water) rho.V.g.OA. rho.Water (W)V.g.OB because m is ρWater (W)If V is rhoWater (W)Is 1 density unit (p)Water (W)Density of water) then: m is 1. V is V; OA is 1 unit length, so ρ is OB. The relation converts the measured solid density into the measured OB length, and the OA is taken as a length unit, and the solid density can be directly read after scales are determined on the cross beam OB. But because of the method for eliminating errors in the structure of the density balance at that time: two fixed pulleys are arranged at two ends of the beam, wound on two thin wires of the fixed pulleys, connected with the water container and the equal-mass balance weight respectively and arranged on two sides of the fulcrum O, so that when the balance is adjusted, equal-arm moment is formed, errors caused by the gravity of the water container are eliminated, the structure is complex, and the assembly and the operation are inflexible, so that the improved density balance is improved, has a simple structure, is convenient to assemble and is more beneficial to operate. The experimental instrument is beneficial to middle school students to carry out integration of physical and mechanical knowledge of junior high school students, training of thinking methods and improvement of practical ability.
Disclosure of Invention
According to the error analysis: 1. the error generated by the self gravity of the water container hung at the right end; 2. when the water is placed in water for drainage, the water attached to the outer surface of the object to be measured influences the solid density measurement accuracy if the object to be measured is taken out of the water for immediate measurement. The improvement method comprises the following steps: 1. will hold the water container itselfThe gravity is converted into partial gravity of the solid to be measured for draining water, so that the density balance has a simple structure and is easy to assemble and operate. 2. The object measured by the experimental instrument is a solid which does not react with water and has density higher than that of water. The device is placed on a carrying net in water, and the device is not taken out of the water in the measurement process and can be read after being directly adjusted to be balanced. The relation in principle changes into (Mg-F) OA Mg OB (F is the buoyancy force applied to the object when the solid to be measured is completely immersed), namely (rho.V.g-rho)Water (W)·V·g)·OA=ρWater (W)V.g.OB (taking ρ)Water (W)The water density sensor is 1 density unit, OA is 1 unit length), rho-1 is OB, namely rho is OB +1, namely if OB is n times of unit length, the solid density is (n +1) times of the density of water, and the ingenious design overcomes the system error caused by that water adheres to the surface of an object when water is drained, and the density is directly measured after the object is taken out of the water.
Drawings
FIG. 1 is a schematic diagram of a density balance, wherein AB is a beam of the density balance, O is a fulcrum of the balance, M is a mass of a substance to be measured at a left end, M is a mass of water discharged when the substance to be measured is completely immersed at a right end, V is a volume of water, OA length is kept unchanged, a hanging position of the discharged water is moved to balance the balance, and rho.V.g.OA ═ rhoWater (W)V g OB (constant OA of 1 unit length, ρ)Water (W)Determined as 1 density unit) the above equation is reduced to ρ ═ OB. This relationship translates the magnitude of the measured solid density into a length of the measured OB.
Fig. 2 is a schematic diagram of a middle school density balance structure. The components in the figure are: the balance comprises a balance base 1, a level meter 2, a level adjusting screw 3, a support 4, a beam 5 with a balance fine adjustment nut, a movable locking wheel 6, a beam balance fine adjustment 7, a boiled water draining container 8, a water overflowing cup 9, a water level valve 10, a water level valve 2, a water carrying net 12, a fulcrum and knife edge 13, a stabilizing frame 14 and a knife edge lifting knob 15.
Description of the action of two water lines: during manufacturing, the mass of water between the two water level lines is just equal to the total mass of the right movable locking wheel 6, the boiled water discharging container 8 and the suspension line thereof, the water level of the object to be measured which is not placed is positioned at the water level line 2, and after the object to be measured is placed, the water level rises, and the water which exceeds the water level line 1 flows into the boiled water discharging container 8. That is, a part of the mass of the water drained by the object to be tested is replaced by the total mass of the movable locking wheel 6, the drainage water container 8 and the suspension line thereof, and the mass of the right suspension (including the sum of the total mass of the movable locking wheel, the drainage water container and the suspension line thereof and the mass of the water drained by the object to be tested overflowing from the water level valve 10) is just equal to the mass of the water drained by the object to be tested. And complex structures such as a balance weight and a pulley do not need to be added to offset useless moment caused by the water container. To increase the sensitivity, the smaller the total mass of the mobile locking wheel 6, the displacement water container 8 and its suspension line, the higher the sensitivity, so this part of the material is chosen as light as possible.
Detailed Description
The middle school density balance is assembled according to the figure 2 (at the moment, the movable locking wheel 6 and the water draining container 8 are not hung), and the base 1 is adjusted to be horizontal. And (II) adjusting the balance of the beam 5 with the balance fine adjustment nut (hereinafter referred to as the beam 5) in no-load: the two water level valves are both in a closed state, water is filled into the overflow cup 9 and exceeds the water level line 1 of the water level valve 10, the carrying net 12 is immersed in the water, the water level valve 10 is opened until the water is level and does not flow, and the water level valve 10 is closed. Rotating the knife edge lifting knob 15 to enable the cross beam to be supported by the cross beam 5, and then adjusting the cross beam balance fine adjustment 7 until the cross beam 5 is balanced. (III) draining: the water level valve 11 is opened to discharge water, and after the water level is settled, the water level valve 11 is closed. The object to be tested is placed in the carrying net 12. The clean drained water container 8 is placed below the water level valve 10, the water level valve 10 is opened to enable water to flow into the drained water container 8 until the water is still and not flowing, and the water level valve 10 is closed. And (IV) measuring, namely, hanging the movable lock wheel 6 and the drained water container 8 on the right side of the beam, rotating the knife edge lifting knob 15 to enable the beam 5 to be supported, and then moving the movable lock wheel 6 to adjust the balance until balance is achieved. And (V) reading, wherein the scale of the suspension line below the right movable lock wheel 6 is the solid density. And (VI) after the measurement is finished, pouring the used water into a water tank, and arranging the instrument.

Claims (3)

1. A middle school density balance characterized by: the density balance structure of the middle school student is a base (1) with a level meter, a support (4) capable of lifting a fulcrum, a cross beam (5) with a balance fine adjustment nut, a carrying net (12) hung at the left end at a unit length position away from the fulcrum, an overflow cup (9) with a double water level valve, and a movable draining and boiling water container (8) hung at the right end.
2. A middle school density balance according to claim 1, wherein: the length of the beam (5) with the balance fine adjustment nut from the fulcrum represents the density, the suspension point on the left side is fixed, the distance from the fulcrum is 1 unit and also represents the density of water, and if the length from the right side to the fulcrum is N units, the solid density is the density of water which is N +1 times.
3. A middle school density balance according to claim 1, wherein: the mass of water between two water level lines of an overflow cup (9) with a double water level valve is just equal to the total mass of the right movable locking wheel (6), the drained water container (8) and the suspension line thereof.
CN202021127340.8U 2020-06-17 2020-06-17 Density balance for middle school students Active CN212514117U (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202021127340.8U CN212514117U (en) 2020-06-17 2020-06-17 Density balance for middle school students

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Application Number Priority Date Filing Date Title
CN202021127340.8U CN212514117U (en) 2020-06-17 2020-06-17 Density balance for middle school students

Publications (1)

Publication Number Publication Date
CN212514117U true CN212514117U (en) 2021-02-09

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CN202021127340.8U Active CN212514117U (en) 2020-06-17 2020-06-17 Density balance for middle school students

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