Rulers Vs. Calipers in This Experiment, You Will Compare the Precision And

In this experiment, you will compare the precision and accuracy measuring the same objects with a ruler and a caliper.

Materials 1 Marble (1) 8 oz. Styrofoam® Cup Ruler Vernier Caliper String 1 Washer

Procedure

Using the ruler, measure the diameter of the marble. Record your measurement in Table 1.

1. Indicate your uncertainty. Record the uncertainty in Table 1. 2. Repeat Steps 1 and 2 for the outer diameter of the washer, inner diameter of the washer, washer thickness, length of the string and the height of the Styrofoam® cup. 3. Repeat Steps 1 - 3 using a Vernier caliper.

Table 1: Ruler and Caliper Measurements

Ruler Caliper Object Measurement Uncertainty Measurement Uncertainty (cm) (cm) (cm) (cm) Marble Diameter 1.0cm 0.05cm 1.20cm 0.0025cm Washer (Outer Diameter) 1.8cm 0.05cm 1.80cm 0.0025cm Washer (Inner Diameter) 0.8cm 0.05cm 0.80cm 0.0025cm Washer Thickness 0.1cm 0.05cm 0.13cm 0.0025cm String Length 5.9cm 0.05cm 5.94cm 0.0025cm Styrofoam® Cup Height 9.1cm 0.05cm 9.02cm 0.0025cm

Post-Lab Questions © 2014 eScience Labs, LLC. All Rights Reserved 1. Compare the measurements for objects using the ruler and caliper and write a general statement on when it is more beneficial to use a ruler rather than a caliper.

Measurements on a ruler are less exact than that on a caliper. Additionally, a ruler would be a more useful when you are measuring a 2D object because the caliper does not lay smoothly against a surface.

2. Comment on accuracy vs. precision for rulers and calipers.

The caliper always give a more precise and accurate reading and you can use one more decimal place because of how exact the measurements are laid out. Accuracy is how close the measurement is to the true value, and because you can measure to a smaller measurement the readings are more exact. The ruler is less exact and so is unable to provide the amount of exactness that a caliper can.

3. What are the sources of uncertainty when using a ruler and caliper?

The smallest graduations on a ruler is 0.1 cm and so taking the half least count in an uncertainty you get (+/-) 0.05cm. The smallest graduations on a caliper is .05mm so using the half least count for this item you have an uncertainty of (+/-) 0.025mm or 0.0025cm.

Before you begin an experiment using the spring scale, you may need to calibrate it. In this experiment, you will become familiar with how to calibrate and use the spring scale.

Materials Mass Set 5 N Spring Scale Roll of Masking Tape 10 N Spring Scale Box of Modeling Clay Stopwatch Single Hole Punch

Procedure

Calibrating a Spring Scale

1. Hold the 5 N spring scale by the handle so that the measurement readings are right side up. This should leave the hook hanging from the bottom. 2. Observe the plunger (the plastic piece hanging from the spring) as you gently pull and release the hook. The top of the plunger that looks like a flat circular piece is called the indicator. 3. To calibrate the spring scale, observe the position of the indicator on the measurement scale. The indicator should rest at 0 g or 0 N when no force is applied (i.e., the hook is not being pulled on by anything). 4. If the indicator is in any position other than zero when at rest, adjust it by twisting the plastic bolt at the top of the spring scale until the indicator rests at the measurement 0 g or 0 N. 5. Repeat Steps 1 - 4 with the 10 N spring scale.

Weighing a Mass

1. Calibrate the 5 N spring scales if necessary. 2. Hold the spring scale upright by the metal handle and hook the stopwatch onto the spring scale hook so it freely hangs. 3. Observe how far the indicator moves on the measurement scale and record the mass in Table 2. 4. Determine and record the uncertainty in Table 2. 5. Repeat Steps 1 - 5 using the 10 N spring scale.