Physics 106/141 - Projectile motion (air table lab) Introduction In this experiment you will be studying two-dimensional

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Physics 106 141 Projectile Motion Air Table Lab Introduction In This Experiment You Will Be Studying Two Dimensional 9 (68.85 KiB) Viewed 46 times

Physics 106/141 - Projectile motion (air table lab) Introduction In this experiment you will be studying two-dimensional motion. As you leared in class, motion in 2D can be separated into 2 one-dimensional problems: one along the x-axis, and one along the y-axis. We will therefore need to be comfortable using vectors and their X- and y-components. We will be using hockey pucks sliding over a nearly frictionless air table to simulate projectile motion. We will obtain a trace that looks like the one shown schematically to the right. Before we start the actual experiment, clearly indicate directly on the figure to the right the following: A useful coordinate system, with the origin located at the initial position of the particle. The range of the projectile (R). The maximum height (hmax). The direction of the particle's initial velocity (0) . An arrow indicating the direction of the particle's acceleration at the top of the trajectory. Experiment - Before continuing on, make sure your TA has shown you the "Introduction to Air Table" video! Make sure the air table is level by placing a puck in the center of the table, turning on the air, and making sure that the puck remains stationary. The heights of the legs of the table can be adjusted. Next, make sure the spark timer is set to 1/60 s. Get a sheet of large graph paper to put over the carbon paper. Practice obtaining a usable trace by giving the puck a push forward while your lab partner simultaneously turns the spark timer on, Turn off the spark timer just before the puck hits the wall. WARNING: Do not touch any metallic portion of the puck when the spark timer is on!

Turn the graph paper over and inspect yo apn paper over and inspect your first trace. Two possibilities are shown below: Above - An example of an UNUSABLE spark trace (points too close together) Above - An example of a good spark trace. Points are clearly separated. In this trace, the groups of seven sparks were chosen so that the highlighted dots occurred ar Al - 1/60 * 68 -0.1 s time intervals. The written values refer to successive times, measured in seconds. air puck table wooden block Now that you have some practice getting a reasonable-looking trace, turn the graph paper over and tape it to the air table surface, making sure that the grid lines are parallel with the edges of the table. Elevate the rear side of the table by placing wooden blocks underneath the back legs (see right, top) bench Turn on the air, and practice projecting the puck up from the lower right hand corner of the paper (right, bottom), so that the puck's path is a large arching curve covering most of the graph paper. The puck must not hit the far side of the air table! After practicing, turn on the spark timer and immediately release the puck to make a spark trace. Turn the paper over and select a reasonable candidate to be the r = 0 dot. Circle the t=0 dot, and then every 6 dot after that. These are the dots you will use to do your analysis.

properties of the puck's trajectory we make any detailed measurements using the trace, let's make some general measurements, and ord them here: Range Maximum height Mae 24.7 Time to get to max height Puck's initial direction (use a protractor) 170.2 Detailed analysis The sample below shows a possible section of the puck's trace. The bold dots indicate the puck's position at time intervals of Ar-0.I s. Sample Point i+1 Point i At = 0.15 Approximate instantaneous velocity at circled dot above (directly in between points i and i+ 1): vs = Ar/A W, = Ay/Ar (Using every 6th dot of trace)

Notice that for each pair of bold dots, we can calculate the puck's X- and y-velocity components, a reasonable measurement of the puck's instantaneous velocity at a point in between the bold do For example, if between bold dots #6 and 7, corresponding to times is = 0.6s and ly = 0.7 s, we measure AX 1.55 cm and Ay2.30 cm, then we would say that at r=0.65 s (a time in between Is and the puck's velocity components are v, -15.5 cm's and v, 23.0 cm's, since Ar-0.1 s always Use the puck's trace to measure Ax and Ay, and record in the table below enough values (with A-015 always!!) to span the whole range of the trajectory (you may not need the whole table). Notice that you need to do a conversion to fill out the table properly! Ax (cm) v. (m/s) C9 0. ay (cm) 2 -3 8 0-18 0.18 V,(m/s) 0-46 1.41 0-31 0.27 0-1 t(s) 0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 0.95 0.18 . 0.11 0.03 0.04 .4 50.$ 018 0:18 0.18. o.18. 0.18 0-04 On 0.10 0. 5 O Lo.42 2.05 235 2.45 2.55 2.65 2.75 2.85 2.95

aph below, plot the v, values from the table as a function of time. Make sure to label your axes ely. The data points should follow a reasonably straight line. Use a ruler to draw a best fitto (DO NOT simply connect-the-dots!). (m/s) 0.1% 0-171 D.16 0415 017| 0-13 0.14 0.05 HIS 0.25 0.5 045 0.55 065 075 0.45 0.95 t(s) 1. Measure the slope of the line, showing your calculation here. Do not forget the units! nie slope- rue = 0.95 - 0 0

Vertical motion On the graph to the right, plot the V, values as a function of time. Again, the data points should follow a straight line. Use a ruler to make a best-fit line for these data points. Vymys 04 O. 0.40 0.78 0-367 + 0-347 2. Measure the slope of the line here, showing your calculation below. Don't forget the units! 0-32 0.30H 0.28+ 0-26- 0.24 0-22- 0.20 0-167 Ouit 0-12 0-10- 0. 1 0-6 3. Compare the 2 slope values you have calculated in #1 and w2. Identify some of the differences you notice (eg., which one is bigger? notice anything about the signs? etc.) 041 0-2 ROTI 02 04 06 0.4 1. 2 463 t(s) 4. Explain how each of the differences you noticed in #3 makes sense. If it doesn't make sense, why not?

ther analysis ng your initial values for V, and Vy calculate the initial direction of the puck's velocity (). howing your work below. A sketch may help 6. Compare your answer in to the one you already recorded in the page 3 table. Do they agree? 7. At this point, we have determined V.. Vys, and a, These 3 variables are enough to determine the pack's trajectory using the kinematics equations. Use the 1" kinematics equation ( v a, A) to determine the time for the puck to reach its maximum height, showing your work below. 8. Compare your answer in #7 to the one you already recorded in the page 3 table. Do they agree? 9. Using whichever ID kinematics equations you want, calculate the range of the projectile, showing your work below. 10. Compare your answer in #9 to the one you already recorded in the page 3 table. Do they agree?

Lab Homework #2 - Projectile Motion Due at the beginning of your lab class Answer all questions. Only some will be graded, for a total of 10 points 1. What will we be using to simulate projectile motion? 2. What should you watch before your experiment? 3. What should you not touch?! 4. What will be the time interval between two adjacent dots on your spark trace? 5. At the bottom of page (1-2), you are told to do what to every 6h dot? (Although, a better option is illustrated in the figure at the top of that same page, because you won't accidentally write-over good dots.) 6. Will your graph of Vavst be a straight line? If so, will its slope be positive, negative, or zero? 7. Will your graph of Vyvst be a straight line? If so, will its slope be positive, negative, or zero? 8. How many variables does one need to know to determine an object's trajectory using the kinematics equations? HW02 projectile.docx Physics 141 Lab