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012–06734A

Smart Timer

27

Mass of Ring

Mass of Disk

Inner Radius of Ring

Outer Radius of Ring

Radius of Disk

Table 4.1. Theoretical Rotational Inertia Data

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

Setup

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.

Procedure

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.

Summary of Contents for ME-8932

Page 1: ...1998 PASCO scientific 7 50 Instruction Manual and Experiment Guide for the PASCO scientific Model ME 8930 012 06734A 09 98 SMART TIMER Plane4...

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

Page 3: ...SpeedMeasurementModes 7 Table 1 Summary of Timing Modes 8 9 AccelerationMeasurementModes 10 Count Modes 10 Test Mode 11 Timing Diagrams 11 LOCK Switch 11 Caring for the Smart Timer 12 Specifications 1...

Page 4: ...he equipment for return shipment will not be covered by the warranty Shipping costs for returning the equipment after repair will be paid by PASCO scientific Copyright Warranty and Equipment Return Pl...

Page 5: ...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 mea...

Page 6: ...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 spo...

Page 7: ...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 Include...

Page 8: ...measurement 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 lin...

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

Page 10: ...essing 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 no...

Page 11: ...iming 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 t...

Page 12: ...Gate Fence Two Gates Pendulum Stop Watch One Gate cm s Collision cm s Pulley rad s Pulley rev s Table 1 Summary of Smart Timer Modes Time Speed Type Modes Key Sequence Timing Diagram Calculation Algor...

Page 13: ...One Gate Linear Pulley Angular Pulley Two Gates 30 seconds 60 seconds 5 minutes Manual One Gate Acceleration Counts Test The key sequences shown are valid in the initial or power on situation only...

Page 14: ...e 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 inc...

Page 15: ...owered 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 Sele...

Page 16: ...ing 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...

Page 17: ...rt 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...

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

Page 19: ...directly To calculate the acceleration from time measurements the following formula must be used Note that Dt is not t2 but is 1 2 t2 see Figure 1 1 Figure 1 1 Explanation of why t2 is used in the for...

Page 20: ...t accuracy 1 The Picket Fence must be dropped at a 90 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...

Page 21: ...g assuming that friction is negligible According to Newton 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 experi...

Page 22: ...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...

Page 23: ...er accomplished in this experiment using the Velcro patches on one end of each cart Procedure PARTA Inelastic Collisions 1 Level the track by setting a cart on the track to see which way it rolls Adju...

Page 24: ...e 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 t...

Page 25: ...e total momentum of the carts before and after the collision and record in the table Questions Table 3 2 Results 1 When two carts moving toward each other have the same mass and the same speed they st...

Page 26: ...ut 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 a...

Page 27: ...al 3 Trial 4 Trial 5 Trial 6 Trial 7 Table 3 4 Results Questions 1 Kinetic energy is not conserved in inelastic collisions but it is conserved in ideal elastic collisions For one of the collisions cal...

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

Page 29: ...theoreticalvalues Theory Theoretically the rotational inertia 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 ra...

Page 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 giv...

Page 31: ...he 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 dist...

Page 32: ...ving 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 rot...

Page 33: ...onal 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 C...

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

Page 35: ...12 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...

Page 36: ...t 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 Ti...

Page 37: ...riment 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 se...

Page 38: ...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...

Page 39: ...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 Titl...

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