Rotary Motion Accessory Pack - Serrata Science Equipment

Sensor AccessoriesRotary Motion Accessory Pack(Product No 3288)Pendulum Rod with two masses, Angular Momentum disc set and Linear Rackwith mini c-clampDATA HARVESTData Harvest Group Ltd1 Eden Court, Leighton Buzzard,Beds, LU7 4FYTel: 01525 373666Fax: 01525 851638e-mail: sales@data-harvest.co.ukwww.data-harvest.co.uk DS 063 No 1© Data Harvest. Freely photocopiable for use within the purchasers establishment.

Rotary Motion Accessory PackIntroductionThe Rotary Motion accessory pack consists of three main accessories that extendthe functionality of the Smart Q Rotary Motion Sensor (Product No 3280).They are:1. The Pendulum Rod - an aluminium rod with two adjustable ring massesand a fixing screw. Can be used with or without the masses to performpendulum and rotational inertia investigations.2. The Angular Momentum disc set - two aluminium discs. Can be used tostudy rotational inertia and conservation of angular momentum.3. The Linear Rack - a 250mm plastic rack with mini c-clamp. Can be usedto measure linear motion over the length of the rack. The c-clamp is forattaching a Smart Q Sensor to the rack.RangesThe calibration for the ranges suitable for use with these accessories is stored inthe microprocessor of the Smart Q Rotary Motion Sensor (Product No 3280). Themethod used to alter the selected range of the Rotary Motion Sensor will dependon the type of EasySense unit. EasySense Advanced and Logger Users can setthe required range using Set Sensor Range option from the units Systemmanagement menu. EasySense Advanced, Flash, Logger, Fast and Real-timeUsers can set the required range using the Sensor configuration application inthe Sensing Science Laboratory program.The Pendulum RodThe pendulum is a predrilledaluminium rod, two adjustablemasses and a fixing screw. Themasses can be adjusted to anypoint on the pendulum rod usingthe thumbscrew fixings.Pendulum Rod2 masses withthumbscrew fixingsFixing screw(3mm x 10mm longwith a M3 thread)For accurate results weigh and record the exact measurement of each componentbefore use i.e.Mass of rod = ____ gm,Length of rod = ____ mm,Mass with thumbscrew = ____ gm.Set the Rotary Motion Sensor to a suitable range e.g. Pendulum.The Rotary Motion Sensor should have the largest of the three-tier pulleysorientated outwards. Use a screwdriver to remove the screw and washer fromthe centre of the pulley wheel.1

Rotary Motion Accessory PackPush the screw supplied in this pack throughthe appropriate hole in the pendulum rod.Position the rod in the locating indents on theouter pulley with the screw in the centre holeof the pulley. Tighten the screw.If a mass or masses are being used in theinvestigation slide onto the rod and tightenthe thumb screw to secure in position.LocatingindentsThree-tier pulleyStudying PendulumsSelect either the Pendulum or Angular position range (Angular position range:0 - 360 degrees, Pendulum: ± 20 degrees).CentrescrewPendulum rodUse the hole at the end of the rod to attach thependulum to the Rotary Motion Sensor.Rotary MotionSensorRest the Rotary Motion Sensor on the bench top toprevent it from moving. Position so that the pendulumrod will hang freely over the surface edge. Clamp theRotary Motion Sensor to a retort stand using its rodattachment.Note: Only the rod should be clamped not the body of the Sensor.With the pendulum hanging freely and stationary, pressthe reset button on the Rotary Motion Sensor to set zero.PendulumrodMass(optional)The pendulum can be used with or without a mass attached. The mass can bemoved up or down the rod to change the effective length of the pendulum.The length of the pendulum is defined as the distance from the point ofsuspension to the centre of gravity of the bob. To find the centre of gravity, placethe pendulum rod/mass rod on a “knife “ edge and find the point at which it isbalanced. Measure the distance from the point of suspension to the centre ofgravity and use this value to give more accurate results.Rod/mass balancedat this pointLength (l)Centreof gravityHole used as apoint of suspension2

Rotary Motion Accessory PackMeasuring rotational inertiaWhen the pendulum rod is used in rotational inertia investigations either theAngular velocity (rads.) or Angular velocity (revs.) range is suitable.Use the hole in the centre of the rod to attach the pendulum to the Rotary MotionSensor.Position the Sensor so the rod can rotate freely in a circular motion. Use with orwithout any masses attached to study rotational inertia.The Angular Momentum Disc setThe angular momentum disc set is comprised of two 2mm thick aluminium discs.Both discs have locating holes that will fit onto the locating pins of the largestpulley of the Rotary Motion Sensor. The primary disc has a central thimble-shapedspindle. The secondary disc has a hole in the centre (that will fit over the spindleof the primary disc) and three friction pads on its lower surface.For accurate results weigh each disc andrecord the exact measurement on the discfor future reference i.e.Mass of primary disc: ____ gmMass of secondary disc: ____ gmDiameter of the discs: ____ mmStudying rotational inertiaSet the Rotary Motion Sensor to a suitablerange e.g. Angular Velocity in radians orrevolutions per second.Mount the Rotary Motion Sensor horizontallywith the largest of the three-step pulleysorientated outwards.Place the primary disc so its locating holesfit over the pins on the outer pulley. Checkthat the Rotary Motion Sensor and disc arelevel.Primary discLocatingpinSecondary discLocatingholesLocatingpin3

Rotary Motion Accessory PackUse the central spindle to manually spin the disc in a clockwise direction. Itshould take at least 30 seconds for the disc to come to a stop.Note: If the disc stops in less than 30 seconds place a drop of light machine oil on to each set ofbearings (see maintenance on page 8).Open Graph from the Sensing Science Laboratory program. From the Newrecording wizard select a suitable timespan and start condition.In this example the start conditionwas set so that data was notcollected until the value from theRotary Motion Sensor (Ang Velrads) fell below 40 rads. SelectStart and a ‘Waiting for Startcondition’ message will show inthe information window. Spin thedisc as fast as possible until thevalue exceeds 40 rads, then leaveto continue spinning. As soon asthe value falls below 40 rads therecording will start.Conservation of angular momentumTo investigate that momentum isconserved in a rotational collisionfollow the steps above, set the startcondition and give the primary disc aspin. When recording has started, waita few seconds, and then drop thesecondary disk onto the primary discwhilst it is still spinning.Select Overlay mode from the DisplayWizard in the Display menu. Click onStart and repeat the procedure severaltimes. The data can be used todetermine the angular speed justbefore and just after the disc was dropped.Primary discSecondary discRound tableThere are locating holes in the secondary disc that fit onto the locating pins on thelarge pulley to produce a flat circular surface. The angular position of an objecte.g. a prism, placed on this surface can be monitored as the disc is rotated.4

Rotary Motion Accessory PackThe Linear RackThe linear rack can be used to measure linear motion over the length of the racke.g. by a force which cannot be tensioned. The rack is 250mm long. It has 80teeth, which are pitched at 3.2 teeth per 10mm.The shaft of the Rotary Motion Sensor is fitted with a gear wheel. The teeth on thelinear rack will engage the gear wheel so that any movement of the rack will rotatethe shaft to convert linear to rotary motion. The calibration for the stored linearrack range is calculated from one revolution of the gear wheel being equal toapproximately 78.5mm length of the linear rack.The linear rack fits into the small square hole that can be found on both sides ofthe Rotary Motion Sensor. Insert the linear rack gently into the hole (from eitherside) with its teeth pointing downwards (towards the shaft of the pulley wheel).Feed in the rack until it just emerges from the square hole on the other side.Square holeLinear rackToothed edgeNote: A small amount of vertical movement allows the teeth on the rack to mesh correctly with the gearwheel. Use this movement to adjust the rack and line up with the exit hole. Do not use force as this maydamage the Sensor.Movement of the linear rack that rotates the pulley in a clockwise direction will givenegative values; in an anticlockwise direction will give positive values.Studying linear movementSet up the Rotary Motion Sensor in a suitable position.Set the Rotary Motion Sensor to the ‘Linear rack’ range.If applicable use the c-clamp to attach a Smart Q Sensor to the linear rack(see page 6).Insert the linear rack into the square hole on the Sensor and feed through untilit just emerges from the other side.Press the reset button on the Rotary Motion Sensor to set zero. If an exact0mm start point is required manually adjust the rack to a zero reading.5

Rotary Motion Accessory PackA mini c-clamp has been provided to enable a Smart Q Sensor to be secured tothe linear rack. Used this way the position of the Sensor can be recorded as it ismoved in an investigation e.g. in an inverse square law investigation with a LightLevel Sensor or Sound Sensor.To use the c-clamp:Place the Smart Q Sensor to beused e.g. a Light Level Sensor, inposition on the side edge of thelinear rack. Open the jaws of thec-clamp and locate over both theSensor and rack so the adjustablescrew will tighten onto the smoothside of the rack.Toothed edgeSmart Q SensorC-ClampNote: Make sure that the clamp does not tighten onto the teeth of the rack.Tighten the clamp gently until the Sensor is secure. Do not over tighten or theSensor case/linear rack could be damaged.Note: To plot one Smart Q Sensor against another e.g. Light against the distance recorded by the RotaryMotion Sensor, select the Display Wizard from the Display menu and then Sensor as the X-axis.Common moments of inertiaThe rotational inertia of a rotating body depends not only on its mass but also onhow that mass is distributed with respect to the rotation axis.i = the rotational inertiam = the mass of the objectr = the radius of the object if spherical/circular.l = the length of the objectThe rotational inertia of a solid disc about a central axis:e.g. the angular momentum disc.i = 1 mr 22Thin rod about axis through centre perpendicular to length:e.g. the pendulum rod fixed at its centre point.Rotation AxislRotation Axisli = 1 m l 2126

SmartTECHNOLOGYQRotary Motion Accessory PackThin rod about axis through one end perpendicular to length:e.g. pendulum rod fixed at its end point.Rotation Axisi = 1 m l 23lRigid body consisting of two massesconnected by a rod of length l andnegligible mass whose rotation axisis through the centre of the mass:e.g. pendulum rod fixed at its centrepoint with a mass attached to eachend of the rod.MassRotation AxislMassi = 1 m l 22Rigid body consisting of two masses connected by arod of length l and negligible mass whose rotationaxis is through the end of rod:e.g. pendulum rod attached using the end hole, witha mass attached to each end of the rod.i = m l 2Example:The ‘moment of inertia’ of the angular momentum discs is calculated from theformula:1 mr22MassSecondary discMass (m) = 136.8gm = 0.1368KgRadius = 75mm = 0.075mr 2 = 0.005625metresThe moment of inertia is = 1 m x r 2 = (0.5 x 0.1368) x 0.005625 = 0.0003847 =0.38 x 10 -3 Kgm 2 2Primary discMass (m) = 150.4gm = 0.1504KgRadius = 75mm = 0.075mr 2 = 0.005625metresThe moment of inertia is = 1 m x r 2 = (0.5 x 0.1504) x 0.005625 = 0.000423 = 0.42x 10 -3 Kgm 2 2lRotation AxisMass7

Rotary Motion Accessory PackMaintenanceIf the Rotary Motion Sensor is not moving as freely as expected place a drop oflight machine oil (e.g. 3 in 1) at the two bearings points:1. On the spindle at the back of the Sensor and2. Between the three-tier pulley and the body of the Sensor.Spin the pulley several times so the oil fully penetrates the bearings.InvestigationsUsing the Pendulum rod and masses:Pendulum investigations e.g. effect of amplitude or mass on periodRotational inertiaUsing the Angular Momentum discs:Conservation of Angular MomentumRotational inertiaCircular MovementUsing the Linear Rack:Linear motion e.g. gas syringe plungerLinear movement of a Smart Q Sensor e.g. inverse square law investigationWarrantyThis pack is warranted to be free from defects in materials and workmanship for aperiod of 12 months from the date of purchase provided it has been used inaccordance with any instructions, under normal laboratory conditions. Thiswarranty does not apply if it has been damaged by accident or misuse.In the event of a fault developing within the 12-month period, the pack must bereturned to Data Harvest for repair or replacement at no expense to the user otherthan postal charges.Note: Data Harvest products are designed for educational use and are not intended for use inindustrial, medical or commercial applications.8

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