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Physics Lab #6 Determining Acceleration in Free Fall I

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Physics Lab #6 Determining Acceleration in Free Fall I Name: ________________________________________ Date: ___________________ Physics Lab #6 Determining Acceleration in Free Fall Introduction: On Earth our motion is influenced by the gravitational pull that the planet exerts on us and on the objects around us. In this lab you will observe the motion of falling objects in order to determine the acceleration due to Earth’s gravity. Materials: Software Video Microsoft Excel Pivot Interactives Video “Free Fall Five” Procedure: 1) After logging in to your computer, open Microsoft Excel. Setting Up Your Spreadsheet 2) In the first column type in the title Time (s) in the first cell (A1). 3) In the second column a. Type in the title Position (cm) in the first cell (B1). b. Type -50 in the second cell (B2). c. Type -45 in the third cell (B3). 4) Left click and hold the mouse button on B2 and then drag the mouse down one cell, so that cells B2 & B3 are highlighted (the values -50 and -45 are highlighted). Then release the left button on the mouse. 5) Move your mouse to the lower right corner of the highlighted box. The mouse icon should change from a white cross to a black cross. 6) Left click the lower right corner with the black cross and drag down to cell B12. The column for Position (cm) should now be filled in with values from -50 to 0 in increments of 5. 7) Type -5 in cell B13. Type -10 in cell B14. 8) Left click and hold the mouse button on B13 and then drag the mouse down one cell, so that cells B13 & B14 are highlighted (the values -5 and -10 are highlighted). Then release the left button on the mouse. 1 9) Move your mouse to the lower right corner of the highlighted box. The mouse icon should change from a white cross to a black cross. 10) Left click the lower right corner with the black cross and drag down to cell B27. The column for Position (cm) should now be filled in with values from -50 to 0 to -75 in increments of 5. Pivot Interactives Videos: 11) Go to the North Tonawanda Senior High School webpage. ntschools.org/nths 12) Click on Teacher Pages near the upper right of the page. 13) Scroll down and click on the link for Mr. Zamojski’s teacher page. 14) Click on Useful Links. 2 15) Scroll down and click on the Pivot Interactives link. 16) On the Log In, enter the email address and password provided on Mr. Zamojski’s teacher page. 17) On the Welcome back page, click on Let’s Go! 18) On the Pivot Interactives Library page, click on the Filter Interactives bar. 19) From the Filter Interactives drop-down menu, scroll down and select Free Fall. 20) Click on the image for Free Fall Five. 21) Once you have the video loaded on your screen, click on the icon in the upper right corner 3 22) Click on both the stopwatch icon and the ruler icon. 23) A clock/counter and ruler calibrations will appear on the screen. You can move the clock/counter on the screen, so that it does not block the video. 24) Press the play button and watch the video once all the way through. 25) After watching the video once press the rewind button to reset the video. 26) Decide which one of the five spheres you want to measure throughout the video. Green Rubber Lead Ball Large Steel Ball Small Steel Ball Styrofoam Ball Ball 1 2 3 4 5 27) Press the play button again and then pause the video until the bottom of your selected sphere has reached the –50 cm marking. You may need to use the Next Frame or Previous Frame buttons. 28) On the clock/counter press the RESET button to set the clock/counter at 0 seconds and 0 frames. 29) Resume the video and record the position at 5 cm increments in your Excel spreadsheet. 4 a. You may need to use the Play/Pause button, Next Frame button, and Previous Frame buttons. 30) Record your time for position 0 cm when the word top appears on the screen. 31) Continue until you have recorded times at for all 5 cm increments up to -75 cm. 5 Graphing: 1) Highlight your data set in Microsoft Excel. 2) Select the Insert tab along the top menu and choose the option to insert Scatter 3) A Position (cm) scatterplot 0 will 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 appear -10 like this one. -20 -30 -40 -50 -60 -70 -80 6 4) Select the Design tab along the top menu and select Quick Layout or Chart Layout. Select the option that gives you a graph with axis labels and a title. 5) Click on the title and change it Mr. Zamojski - Position vs. Time to read Your Name – 0 Position vs. Time 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 6) Click on the vertical axis and -10 change it to read Position -20 (cm). 7) Click the horizontal axis and -30 change it to read Time (s). 8) Click on the LEGEND to the -40 right and delete it. Your Position Position (cm) graph should now look like -50 this. -60 -70 -80 Time (s) 9) As you can see this a parabola. A linear fit (y = mx + b) does not fit the data well. Therefore, for free fall position (x) is not proportional to time (t), and we will have to alter the variables to get a better relationship. b. Since the data has the shape of a parabola, this indicates the spheres are experiencing constant acceleration, which may be modeled better by a Velocity-Time graph. 10) Right click on the B column. The whole column will be highlighted and a menu will pop up. Select Insert from the menu. 7 11) An empty column will appear in column B between your Time (s) column and your Position (cm) column. 12) In the first cell of column B type in Velocity (cm/s) in B1. 13) Leave on cell B2 blank. The formula for velocity is 푑푖푠푝푙푎푐푒푚푒푛푡 ∆푥 푥푓푖푛푎푙 − 푥푖푛푖푡푎푙 푣 = = = 푡푖푚푒 ∆푡 푡푓푖푛푎푙 − 푡푖푛푖푡푖푎푙 14) Click on cell B3. Type in the following formula to calculate velocity: =(C3-C2)/(A3-A2) 15) Press enter. Excel automatically calculates the value based on the equation you entered. 16) Move your mouse to the lower right corner of the highlighted box. The mouse icon should change from a white cross to a black cross. 17) Left click the lower right corner with the black cross and drag down to cell B27. The column for Velocity (cm/s) should now be filled in with calculated values from for each time. 8 18) Highlight your data in columns A and B (Time (s) and Velocity (cm/s)) in Microsoft Excel. 19) Select the Insert tab along the top menu and choose the option to insert Scatter. 20) A scatterplot will appear Velocity (cm/s) like this one. 400 21) Left click and hold your 300 graph and drag it, so that 200 it does not cover your 100 data or your other graph. 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 -100 -200 -300 -400 -500 22) Select the Design tab along the top menu and select Quick Layout or Chart Layout. Select the option that gives you a graph with axis labels and a title. 9 23) Click on the title and Mr. Zamojski - Velocity vs. Time change it to read Your 400 Name – Velocity vs. 300 Time 24) Click on the vertical 200 axis and change it to 100 read Velocity (cm/s). 25) Click the horizontal 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 axis and change it to -100 read Time (s). (cm/s) Velocity 26) Click on the LEGEND -200 to the right and delete -300 it. Your graph should now look like this. -400 -500 Time (s) 27) Right click on one of the data points and your graph and select Add Trendline. 28) In the menu that pops up check the boxes for 29) Close the Format Trendline menu. Mr. Zamojski - Velocity vs. Time You should now have a line on 400 your graph with an equation and an R2 value. 300 y = -993.75x + 331.65 200 R² = 0.9975 100 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 -100 Velocity (cm/s) Velocity -200 -300 -400 -500 Time (s) 30) As you can see a linear fit is much better than before. Therefore, velocity is proportional to time for free fall. 푣 ∝ 푡 10 .
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