Significant Figures Lab Instruction SheetPage 1/2
Purpose
This lab will give you a better appreciation of how our measurement error is a function of the tools that we use to make our measurements.
1) You will get practice recording data using the right number of significant figures
2) You will get practice using significant figures multiplication rules
3) You will also use graphical techniques to determine physical properties.
Linear Density
The concept of density (also called volume density) is explained in the sample physics lab on density that was provided separately. In this case, we will measure a different kind of density: density per unit length for metal chains. We will call this the linear density, , of the chains. (This is the Greek letter: rō.)
, where m is the mass of the chain and L is the length of the chain.
Since the chains are fairly uniform in their composition we should expect that:
The linear density of the chains should not be a function of the length. You will test this hypothesis as well.
Materials
1 Bag containing three lengths of chain, special meter stick with varying degrees of precision, balance
Procedure
1)You will make three measurements of the length of each piece of chain and two measurements of the mass of each piece of chain.Each measurement will be made with a different scale.Always measure with the least precise scale first and then increase the precision. In each case, express your answer with the appropriate amount of significant digits based on the measurement tool.
2) You will have to figure out how to deal with the fact that the chain may not be straight, and that the end points may be difficult to measure accurately.
3) How the scale used impacts the significant figures:
You always end up with one more significant figure than available due to the lines on the scale
Measured value: 22.4 cm Measured value 22 cm
4) Notice that when making measurements, the zero position must be carefully checked. Many rulers do not have the zero at the very edge of the ruler. Also, some rulers have broken ends.
5) All of your measurements for this lab will be in cm and g. At the end of the lab you will do a conversion to m and kg.
6) More details about measurements.
a) You will have to make a number of measurements, so have one person using the scale while another person is using the meter sticks.
b) The special meter stick is 1 m long. There are 100cm in a meter. Be careful to record all of your measurements with appropriate units.
c)When measuring length
i) first use the scale where the meter stick is divided into 10 segments
ii) this is the 0.1m scale
ii) next use the 0.01m scale
iii) finally use the 0.001 m scale
d) When making mass measurements
i) you will not need to use the heaviest slider
ii) for the first measurement, keep the smallest slighter set to zero, and only use the top slider. For this measurement you may move the slider between the fixed indents to help you estimate the value
iii) for the second measurement, use both the top slider – using the indents, and use the smallest slider
7) Data Analysis is described within the worksheet.
8) In the conclusion section
a) You will not need a percent error for this lab.
b) Follow the worksheet.
9) Do the extension problem in the lab.