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012–06734A

Smart Timer

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Accounting for Friction

1.

Set up the Smart Timer to measure

 Speed, Pulley (rev/s)

.

2.

Tie several paper clips onto the string that hangs over the Smart Pulley.

3.

Start the disk spinning slowly.

4.

Adjust the hanging mass (number of paper clips) until the speed remains constant.

5. 

 Record this “friction mass” in Table 4.2.

6.

Repeat for each setup below: ring and disk combined, disk alone, and disk vertical.

Measurements for Determining the Rotational Inertia Experimentally

1.

Set up the Smart Timer to measure

 Acceleration, Linear Pulley (cm/s

2

)

.

2.

Find the acceleration of the ring and disk using a hanging mass of about 50 g. Wind the
thread up and let the mass fall. Record the acceleration (press 

) when the mass has

fallen about 1/3 of the total fall distance (to minimize the effect of friction). Repeat at

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1.

Place the disk directly on the center shaft as shown in Figure 4.3. The side of the disk
that has the indentation for the ring should be up.

2.

Place the ring on the disk, seating it in this indentation.

3.

Mount the Smart Pulley to the base and connect it to channel 1 or 2 of the Smart Timer.

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Measurements for the Theoretical Rotational Inertia

1.

Weigh the ring and disk to find their masses and record these masses in Table 4.1.

2.

Measure the inside and outside diameters of the ring and calculate the radii 

R

1

 and 

R

2

.

Record in Table 4.1.

3.

Measure the diameter of the disk and calculate the radius 

R

 and record it in Table 4.1.

Содержание ME-8930

Страница 1: ... 0 1 23456 Instruction Manual and Experiment Guide for the PASCO scientific Model ME 8930 6 78693 6 SMART TIMER ...

Страница 2: ...Smart Timer 012 06734A ...

Страница 3: ... 1 F 1 1 A922 6 G H 6 A 1 1 C 6 I C 6 J A 6 C 91 C 6 K L A9 10 2 C 6 MNO G 1 C 91 C 6 P 9 C 6 P C 6 2 Q 21 R S AT 3L 1 2 1 3 A 1 1 U A U G 10 U 1 9 3 2 B 7V 1 L G 1 W1 H 0 I 7V 1 T L X T Y A 6 R T K 7V 1 31 L 1H C 9 O 7V 1 Z 91L 1H G 29 1 C 9 UI 3 1 A922 6 7V 1 3 A9 1 E H 1 ...

Страница 4: ...9 9 1 1 0 E 6 1 H 6 2 6 3 6 2 1 1 23 1 6 Q 2 9 6 0 1 1 E 2 3 89 1 1 91 3 T H 1 6 0 3 T 11 0 A3 2 1 1 91 2 3 89 1 1 1 T 6 0 GA 012 34 54 2 Z 1 69 3 9 9 _ 3 01 23 1 1 T Equipment Return A3 9 6 3 1 69 3 H 1 91 6 GA 1 0 1 4 0 GA 0 14 3 4 1 V 7Z 7 1 91 2 3 1 69 a 4 3 1 91 9 3 1 b 6 3 2 19 T 1 0 9 6 X 7Da C7X 5 RR 7 G 7 7Q Z 7 a X 5 a GX Ga cG X Z C GA 53 1 91 2 89 1 1 14 3 9 9 E 6 1 1 0 11 1 T 1 0 1 6 ...

Страница 5: ...r existing timing options The Smart Timer s internal microcontroller also eliminates the problem of incorrect readings due to multiple passes through the same photogate by understanding the type of measurement selected and ignoring multiple passes The Smart Timer has many different options for timing and calculating values based on inputs from a variety of sensors The graphics on the keypad aid in...

Страница 6: ...d to a glide or Dynamics Cart the Smart Timer and Smart Pulley can be used to determine linear acceleration cm s2 as well Note The use of pulleys with different diameters and or different number of spokes than the Smart Pulley or the ME 9450 Super Pulley will give incorrect results in the speed and acceleration calculations Power Options The Photogate Timer can be powered using the included 9VDC a...

Страница 7: ...adapter liquid crystal display touchpad keys mode illustrations on off switch side panel battery compartment bottom panel input channel 2 input channel 1 connector for 9VDC adapter side panel 9 VDC adapter Figure 1 Included equipment Smart Timer Picket Fences 5 cm fence 1 cm fence 1 cm flag ...

Страница 8: ...asurement until both the type and mode have been selected 3 Once a complete measurement has been selected press Start Stop to begin You will hear a beep and a asterisk will appear on the second line of the display In most modes the indicates that the Smart Timer is now waiting for an event to occur like a fence passing through a photogate 5 If an event occurs the Smart Timer beeps again displays a...

Страница 9: ...012 06734A Smart Timer 5 ...

Страница 10: ...ressing Start Stop will stop the measurement and any recorded times will be displayed Two Gates In this mode the Smart Timer measures the time between blocking two photogates This mode is useful for not only air tracks and Dynamics Tracks but also with the ME 6810 Time of Flight Accessory In this mode you must plug the photogate you expect to encounter first into input channel 1 and the second pho...

Страница 11: ...timing with the Start Stop key and end it with a photogate block or vice versa 4 If a photogate is plugged in and blocked when you try to use the Start Stop key as a stopwatch the Smart Timer will be timing the photogate and waiting for the photogate to become unblocked So when you push the Start Stop key the asterisk disappears and when you push the Start Stop key again the asterisk reappears No ...

Страница 12: ... 0102 3 4 5 6 7 28 9 11 7 28 9 011 7 8 9 011 7 8 9 0 1 2 3 4 0 121 3 415365200 758 8591 83 619 2 ...

Страница 13: ... 011 A01 011 BC DC E 2 0 F 0 1 0 1 2 2 0 1 234 3 5 3 353 2 0 6 07 8 35 53 2 9 ...

Страница 14: ...ke the radians second measurement there is a two second maximum time for two photogate blocks translating to a minimum speed of 0 05 rev s Also note that accuracy decreases rapidly as pulley speeds increase above 600 rpm At 600 rpm accuracy is 1 Acceleration Modes One Gate The Smart Timer uses the time measurement between two equally spaced 5 cm block unblock block sequences to calculate average a...

Страница 15: ...powered as long as the top line of the display reads Test Gates This mode is useful for experiment setup or for testing accessory photogates G M tubes or other Smart Timer accessories Pressing the Select Measurement key will exit the test mode and remove power to the external device The display graphics depict a blocked photogate as a vertical line and an unblocked photogate as an arrow Timing Dia...

Страница 16: ...ming resolution of the Smart Timer is 100 microseconds in all modes except Stopwatch which is 10 ms Calculated Values Calculated values are displayed to one or two decimal places with typical accuracy being 1 in the least significant digit For extremely high speeds such as might be generated by hand spinning a Super Pulley accuracy is degraded for calculated parameters because of the very short ti...

Страница 17: ...art Timer so you get more accurate measurements of the free fall time of the steel ball See page 34 Determining the acceleration due to gravity g with the Free Fall Adapter and Figure 10 1 for details of the setup Laser Switch ME 9259A This highly collimated photodetector is identical to a photogate except that a laser available separately is used as the light source With the Laser Switch the moti...

Страница 18: ...Smart Timer 012 06734A 14 ...

Страница 19: ...eleration from time measurements the following formula must be used Note that t is not t2 but is 1 2 t2 see Figure 1 1 Figure 1 1 Explanation of why t2 is used in the formula for calcu lating g V1 V2 Δ t Δt 1 2 1 2 t1 1 2 1 2 t2 t1 1 2 1 2 t1 1 2 1 2 t2 1 2 1 2 t1 Δt 1 2 1 2 t2 6 6 PART A Determining the acceleration from time and distance measurements 1 Mount the photogate on a stand or hold the ...

Страница 20: ...t accuracy 1 The Picket Fence must be dropped at a 90º angle to the photogate beam in such a way that it does not rotate on the way down One method to improve the drop is to hold the edge of the Picket Fence with a clothspin or binder clip and drop the fence by squeezing the clothespin or clip 2 The Picket Fence must be dropped so the 5 cm marks cut the photogate beam 3 The Picket Fence must pass ...

Страница 21: ...ton s Second Law this net force should be equal to ma where m is the total mass that is being accelerated which in this case is m1 m2 This experiment will check to see if m2 g is equal to m1 m2 a 6 6 1 Level the track by setting the cart on the track to see which way it rolls Adjust the leveling screw at the end of the track to raise or lower that end until the cart placed at rest on the track wil...

Страница 22: ... Timer once the car has started moving The timing will begin when the photogate beam is first blocked Repeat this measurement 3 times with the same masses Record all the values in Table 2 1 Calculate the average accelerations and record in Table 2 1 9 Increase the mass of the cart using the bar mass and repeat the procedure 58 1 1 Calculate the measured force F m1 m2 a and record in Table 2 1 2 Ca...

Страница 23: ...periment using the Velcro patches on one end of each cart 6 6 PARTA Inelastic Collisions 1 Level the track by setting a cart on the track to see which way it rolls Adjust the leveling screw at the end of the track to raise or lower that end until a cart placed at rest on the track will not move 2 Put a Picket Fence into the slots in the top of each cart and place the Collision Carts so the Velcro ...

Страница 24: ...ic collisions Equal Masses a Place one cart at rest in the middle of the track Give the other cart an initial velocity toward the cart at rest b Start both carts at one end of the track Give the first cart a slow velocity and the second cart a faster velocity so that the second cart catches the first cart Unequal Masses Put two mass bars in one of the carts so that the mass of one cart 3M is appro...

Страница 25: ... For each of the cases calculate the percent difference between the total momentum of the carts before and after the collision and record in the table 91 1 When two carts moving toward each other have the same mass and the same speed they stop when they collide and stick together What happens to each cart s momentum Is momentum conserved Explain 2 Kinetic energy is not conserved in inelastic colli...

Страница 26: ... Masses Put two mass bars in one of the carts so that the mass of one cart 3M is approximately three times the mass of the other cart 1M Weigh the carts and record the masses in Table 3 3 a Place the 3M cart at rest in the middle of the track Give the 1M cart an initial velocity toward the cart at rest b Start the carts at opposite ends of the track at approximately the same speed toward each othe...

Страница 27: ...1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 0 91 1 Kinetic energy is not conserved in inelastic collisions but it is conserved in ideal elastic collisions For one of the collisions calculate the percentage of the kinetic energy that is lost in the collision Was kinetic energy conserved Explain your results ...

Страница 28: ...Smart Timer 012 06734A 24 ...

Страница 29: ...tia I of a ring about its center of mass is given by where M is the mass of the ring R1 is the inner radius of the ring and R2 is the outer radius of the ring See Figure 4 1a The rotational inertia of a disk about its center of mass Figure 4 1b is given by where M is the mass of the disk and R is the radius of the disk The rotational inertia of a disk about its diameter Figure 4 1c is given by I 1...

Страница 30: ...rT where r is the radius of the 3 Step Pulley about which the thread is wound and T is the tension in the thread when the apparatus is rotating Applying Newton s Second Law for the hanging mass m gives See Figure 4 2 Σ F mg T ma Figure 4 2 RotationalApparatus and Free Body Diagram rotational disk A base hanging mass mg T a Solving for the tension in the thread gives Once the linear acceleration of...

Страница 31: ...nd disk using a hanging mass of about 50 g Wind the thread up and let the mass fall Record the acceleration press when the mass has fallen about 1 3 of the total fall distance to minimize the effect of friction Repeat at 9 1 Place the disk directly on the center shaft as shown in Figure 4 3 The side of the disk that has the indentation for the ring should be up 2 Place the ring on the disk seating...

Страница 32: ...can be subtracted from the total leaving only the rotational inertia of the ring To do this take the ring off the rotational apparatus and repeat step 2 using a hanging mass of approximately 30 g 5 Remove the disk from the shaft and rotate it up on its side Mount the disk vertically by inserting the shaft in one of the two D shaped holes on the edge of the disk See Figure 4 4 6 Repeat steps and 2 ...

Страница 33: ... rotational inertia of the disk from the total rotational inertia of the ring and disk Note This calculation will be the rotational inertia of the ring alone 5 Calculate the experimental value of the rotational inertia of the disk about its diameter 6 Calculate the theoretical value of the rotational inertia of the ring 7 Calculate the theoretical value of the rotational inertia of the disk about ...

Страница 34: ...Smart Timer 012 06734A 30 ...

Страница 35: ...r 012 05035 Acceleration Down an Incline Experiment 8 Use a Photogate and the Smart Timer instead of a stop watch Figure 5 1 Adjust the height of the Photogate so the light path is intersected with the 5 cm fence of the Smart Timer fences Set up the Smart Timer to measure Acceleration One Gate Press to activate the Smart Timer and release the cart Photogate Head To Smart Timer Photogate mounting b...

Страница 36: ...rt oscillations and activate the Smart Timer to measure the period of oscillation Note The following experiment is in copy ready form in the manual for the Introductory Dynamics System with Computer Timing Kit manual number 012 04894 Conservation of Energy Experiment 8 Use a Photogate and the Smart Timer instead of a computer and IDS Timer software and set the experiment up as directed in the expe...

Страница 37: ...eriment 2 Use the Smart Timer instead of a computer and IDS Timer software and set the experiment up as directed in the experiment Plug the photogates into the Smart Timer as shown in Figure 8 1 and set up the Smart Timer to measure Time Two Gates Press to activate the Smart Timer and fire the launcher Calculate the initial velocity using the time required for the ball to pass through the photogat...

Страница 38: ...1 or 2 of the Smart Timer Figure 10 1 Set up the Stopwatch mode of the Smart Timer Press once The Smart Timer is now activated and will record the time the interval between the release of the ball and the contact of the ball with the receptor pad of the Free Fall Adapter to Smart Timer channel 1 or 2 receptor pad steel ball support rod and base ball release mechanism controller box of the Free Fal...

Страница 39: ...w pasco com Contacting Technical Support Before you call the PASCO Technical Support staff it would be helpful to prepare the following information If your problem is with the PASCO apparatus note Title and model number usually listed on the label Approximate age of apparatus A detailed description of the problem sequence of events incaseyoucan tcallPASCOrightaway you won t lose valuable data If p...

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