OL-02 Density Measurement - Take data from video of experiment (1)

OBJECTIVES In this laboratory experiment, the following objectives will be achieved: (i) Determination of densities of three metal cylinders, a rectangular solid, an irregular shaped solid, and a copper wire, by finding their volumes and masses. (ii) Identifying the materials by comparison of densities with the accepted values. EQUIPMENT 1. Triple- beam balance 2. Vernier Caliper 3. Micrometer 4. Electronic Balance 5. A ruler (inches and centimeters) 6. Graduated Cylinder 7. A roll of copper wire. 8. Wire Cutter 9. Irregular object (lead, zinc, etc.) 10. Three cylindrical metals (brass, iron, aluminum, steel, tin, zinc, etc.) and copper wire. INTRODUCTION: Physics is a science of measurement that involves measurements of various parameters. Therefore, we need to learn how to take accurate measurements and how to use these numbers for calculations. In any measurement the uncertainty associated with it and the number of significant figures should be of particular interest to the experimenter. It should be underlined that the number of significant figures to be kept in a reading depends on the measuring device used. In this experiment the dimensions of various objects will be determined by means of a meter ruler, a Vernier caliper, and a micrometer caliper and the probable error in these measurements will be determined. The mass of each object will be measured with a triple beam balance (or electronic balance if available) and the density of each object as well as the material from which it is made will be determined. Density is the measurement of the compactness of matter in a substance. This might be done experimentally by measuring the mass and obtaining the volume of the substance. The volume may be obtained depending on the shape of the substance. For example, if the substance is cylindrical in shape then its volume can be computed from the equation V = πr 2 h , where h is the height or length of the substance. If the material is shaped like a sphere, the density is 3

Figure 2 c) Micrometer It is used to measure very small thicknesses and diameters of wires and spheres. It consists of a horizontal scale along a barrel divided into millimeters and a circular scale that has 50 divisions. The thimble has a scale of 50 equal divisions, each division is 0.01mm. (Figure 3). The Least count = 0.5 mm / 50 = 0.01 mm = 0.001 cm. Figure 3 To take a measurement using the micrometer, place the object to be measured between the anvil and spindle. Grip the ratchet and turn until the object is lightly gripped. DO NOT OVERTIGHTEN. The first part of the measurement is taken from the sleeve. Each division is 0.5 mm (note that the millimeters and half millimeters are on opposite sides of the line). Care is needed as the thimble may partially obscure this reading, particularly when the thimble reading is close to zero. In the diagram the reading on the sleeve is 6.5mm. Note that the ‘0.5’ mark is just showing. The thimble reading must now be added to this. In the diagram the line on the sleeve is in line with the seventh division on the thimble, showing 0.07 mm (each division being equal to the least count). The total reading is therefore 6.5 + 0.07 = 6.57 mm. EXPERIMENTAL PROCEDURE 1) Determine the mass of each cylinder, the copper wire and the irregular solid. 2) Determine the zero reading of the Vernier caliper. This is when the jaws are in contact with each other. In this condition, the reading should be 0.00 cm. A non-zero reading is the zero error of the instrument. If the value is less than zero, the zero error is negative. Record the values in centimeters. Make sure to open and close the jaws before each measurement. 6

Part III. Determination of Mass with Electronic Balance 1 2 3 4 Average Reading – Zero Error Zero error of triple beam / electronic balance 0.00 g 0.00 g 0.00 g 0.00 g 0.00 g X Mass of cylinder-1 58.0 g 56.0 g 54.0 g 56.00 g 56.0 g 56.00 g Mass of cylinder-2 22.00 g 20.00 g 22.0 g 18.00 g 21 g 21.0 g Mass of cylinder-3 208 g 206 g 206 g 208 g 207 g 207 g Mass of rectangular solid 66.0 g 66.0 g 68.0 g 66.0 g 67 g 67 g Mass of irregular object 66.0 g 66.0 g 66.0 g 66.0 g 66.0 g 66.00 g Mass of copper wire with Electronic balance 0.00 g 0.00 g 0.00 g 0.00 g 0.00 g 0.00 g Part IV. Determination of Volume of Irregular Solid using Overflow Can 1 2 3 4 Level before immersion 15.0 mL 29.0 mL 15.0 mL 15.0 mL Level after immersion 41.0 mL 53.0 mL 37.0 mL 38.0 mL Average Volume Volume of solid 26.0 mL 24.0 mL 23.0 mL 23.0 mL 24 mL Part V. Calculation of Density Object Mass g Length cm Radius cm Volume cm 3 Computed Density g/cm 3 Material of object Accept ed Density g/cm 3 Percent error in density Cylinder-1 56 g 5.01 cm 0.635 cm 6.35 cm3 8.82 g/cm3 steel 8.96 g/cm3 1.56% Cylinder-2 21 g 6.33 cm 1.12 cm 24.7 cm3 0.829g/cm3 Aluminu m 0.860 g/cm3 3.60% Cylinder-3 207 6.33 cm 1.12 cm 24.7 cm3 8.38g/cm3 brass 8.73 g/cm3 4.00% Rect. Solid 66.5 g x x 8.00 cm3 8.31 g/cm3 zinc 8.73 g/cm3 4.81% Copper Wire Irregular Solid 66.0 g x x 24.0 cm3 2.75 g/cm3 lead 2.70 g/cm3 1.85% 9

POINTS TO THINK ABOUT 1. Why is each measurement taken more than once? -It takes more than once because it eliminates the errors and any confusion from a single measurement. It also avoids the human errors and instrumental errors. 2. Why was micrometer used instead of Vernier caliper for measuring the diameter of the wire? -The reason why micrometer was used is because it is more precise and accurate then the vernier caliper 3. What is the “least count” of the measuring devices used? -The least count is the lowest limiting value of the measuring instrument. 4. How can you get the density of an irregular shaped object? -The equation of density is D= m/V the mass can be measure on scale or balance, the volume of an object can be measure by immersing it in water a beaker or some other container that has a volume marking 5. Was the cross-section of the wire circular? 6. What is the effect of kinks in the wire? - The effect would not only damage the insulation of the wire but it can also crack or slightly bend. 7. Why is electronic balance used for the wire, but not for the cylinders? - Electronic balanaces provides an accurates and precise measurement of weighth of materials. 8. Can you identify the material by knowing the density and appearance? Yes, it can be identify an unknown substance by measuring its density and comparing the results with a list with knowing densities to compare it. 9. How tight should the micrometer and Vernier be made while making measurements? - They both needs to be tight enough so whenever you touch it the measurement would be as accurate is possible and it would be no error 10. What are the equations for volume of a cylinder, cube and sphere? The volume equation for a cylinder is π × r2 × h = 2 π × r3 The volume of cube V=a3 The volument equation for sphere 4 3 π × r3 11. How would you calculate the mass of an object if its density is known? -Density = mass/volume so to calculate mass you would do density x volume 12. To how many decimal places in cm can the Vernier and micrometer read? -Up to 2 decimal places 13. To what place of decimal can the triple beam balance read? - 2 decimal places 14. What range of errors are “acceptable”? The acceptable range error is 1-5% 12