At this point, DOUBLE CHECK to make sure that all data entries are expressed in SI units (meters, kilograms, seconds).

1.  In cell C30, enter the number "1". You need a serial number for each trial, so begin with mouse down at C30 and drag down through cell C36. Then use EDIT...FILL...Series. Click OK on the dialog box, and C30:C36 should contain the number of washers used in each trial (1 through 7).

2.  In cell E30, enter "= C30 * $G$11 * 9.8" to calculate the washer's weight in trial 1. This calculation takes the number of washers used in this trial and multiplies by the mass of each washer times the acceleration due to gravity to give the weight of the washer. Use EDIT...FILL....Down as before to populate cells E30:E36.

3.  Use the mouse to select all the cells from D30:E36, that is all the acceleration and falling mass data, including the headings.

• Select the x-y scatter icon from the top Toolbar.

• Click on the chart itself.

• Click on the legend and hit Delete.

• From the View menu, select the Formatting Palette if it is not already present.

• Select Chart Title from the Title pull-down menu and fill it in.

• Next select titles for the Horizontal and Vertical axes and fill them in.

• Use the mouse to size the chart and to locate it from cells B41 to I60.

4.  Click on any one of the data points.

• Choose Chart...Add Trendline from the menu.

• Under the Options tab, choose Display equation on chart. The equation of the best straight line fit to the data will appear on the chart.

5.  From this fitting equation, record the values of the slope and the intercept in cells F62 and F64, respectively. Ideally, the slope should be equal to the total mass of all 7 washers plus the glider. We know however, from Equation (1) in the Introduction that the "effective" mass of the pulley also enters in as part of the slope.

HINT: You can set up the spreadsheet to calculate this value: the total mass is recorded in cell G13, and the fitted value in F62.

• Select cell F66, where the answer is to appear.

• Type "=ABS(G13 - F62)/G13 * 100". The ABS function takes the absolute value of the difference. The difference is then divided by the measured value and multiplied by 100 to give a percentage.

6.  Answer Questions 1 through 4 on the Worksheet.