G By Freefall Experiment Using the PASCO Smart Gate

Dr. Nichola Swann will walk you through the G By Freefall experiment and how to do it in the most cost-effective way using PASCO scientific equipment. Make sure to watch until the end for extra tips!

You are going to need a Retort stand, a clamp, a big G-clamp, a PASCO Wireless Smart Gate, a picket fence and something to cushion the floor of the picket fence when you drop it. You’re also going to need a device or a computer to collect your data on and some PASCO software.

Video transcript below:
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Hi, I’m Nichola from LaBLiFe

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I’m filming today on location
at Keele University and in this video I’m

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going to walk you through the G By Freefall experiment and how to do it

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in the most cost-effective way
using PASCO scientific equipment.

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Okay.

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So in terms of equipment,
you are going to need a

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Retort stand, and a clamp, a big G-clamp

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a PASCO Wireless Smart Gate

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a picket fence,

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something to cushion the floor
of the picket fence when you drop it.

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As an example on the floor, I have got
a big plastic box full of bubble wrap.

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You’re also going to need a device
or a computer

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to collect your data on and some PASCO software.

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The software that I’m going to be using
today is SPARKvue

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It’s PASCO’s entry-level software
and it’s also completely free for Apple,

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Android and Chrome devices.

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Okay.

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So you’ll see from the

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setup that I position this retort stand
in such a way that I can clamp it

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really nicely to the table

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and I can also suspend
the Smart Gate over the edge of the table.

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The point of the experiment
is that I’m going to be dropping

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this picket fence through the gate.

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So you will see on here that this got
black sections and clear sections

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So as each of these black sections passes
through the gate, it’s

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going to break the beam

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and this gate is going to give us velocity
readings for each of these sections.

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So as the first section passes
through the gate, it’s

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going to be traveling
at a certain velocity.

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And then because this thing
is accelerating due to gravity,

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the next section is going to be traveling
slightly faster at a higher velocity,

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high velocity still, and so on
and so forth as we travel up the gate.

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So what we’re going to

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get the software to do is plot
those velocities as a function of time,

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then take a linear fit.

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So basically look at the rate of change
of those velocities

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and then the gradient of that linear fit
is going to give us our value for G.

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So relatively nice and easy.

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It’s a really nice experiment

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to start introducing when you’re thinking
about calculus and differentiation,

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it’s really going to hammer home
that differential relationship between

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velocity and acceleration.

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Right…

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So all that’s left to do now is pair

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our sensor to the PC
and get the software up and running.

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So what I’m going to do
is turn this thing on.

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So the status LCD on the front of
the unit is now flashing red,

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showing that it’s on
and ready to pair.

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Here is our SPARKvue home page.

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I am going to click on sensor data.

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It’s going to look
for the PASCO devices in the room

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and it has found a Smart Gate

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It’s got this unique ID code here,
which is going to match the unique ID code

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on the front of the unit.

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I am going to click on it to connect

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and once it’s connected, the status
LED on the front of the unit

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is going to flashing
green, showing it successfully paired.

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Okay, so we just need to tell the software
what we want the smart gate to do.

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So I’m going to click on this config
wheel over here.

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I’m going to tell it I’ve got a Smart Gate
only and I want to use it with a picket fence.

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Click here and tap okay,

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it’s asked me for the flag spacing.

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So just to clear up what that is

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you can see that we’ve got black sections
and clear sections, the flag spacing

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is those two sections combined, which
using a ruler I know is five centimetres.

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And so we’ve got 0.05 meters here,
which is equivalent to five centimetres.

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So all I need to do is click, okay,

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I want it to give me velocity readings, and
I want it to give me a graph

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Click on here…

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So this is pulled up a graph of velocity
on the Y axis again time on the X

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we are in SI Units so we don’t need to do
any messing around with units afterwards.

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So now all I need to do is press start.

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It doesn’t matter if you’ve got a lag
at the beginning of your data collection.

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What I’m going to do
is I’m going to hold the picket fence

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above the gate and then I’m just going to
drop it through.

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I want to make sure it’s nice parallel

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whoop…

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There you go.

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Stop data collection.

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And I’m going to use this tool
here in the graph tools

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just to scale to fit, auto scale the data.

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Oh, it’s actually
a little bit wonky, interesting.

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And so I’m going to click here for Linear
Fit, and see what gives us

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So M is the gradient giving us 9.76,
which isn’t too bad

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Lets start to update my Excel spreadsheet

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and I can put my data in here
and we’ll do a few runs and calculate an error

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So values for G in metres per second.

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Squared

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9.76

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Okay it’s trying again

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I’m going to press start again

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pick this up

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and pass it through.

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It definitely rotated that time
so it might not be very accurate.

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Again, let’s see, press stop.

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He has got a bit of a wonk on at the end

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Let’s linear fit
and have a look. 9.89.

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Still not too bad

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Log it in here

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and press start again.

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Right, going to do it really carefully this time
and try and not to get it to rotate.

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That was a good one. Let’s have a look

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Auto scale again.

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Oh yeah, perfectly straight.

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And then press here.

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9.77, so

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I think that’s probably okay.

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Shall we do what our mean is out of those?

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So if I go for equals average

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9.806 recurring, that’s perfect.

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And then error wise we can do

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the standard deviation of our results
divided by route N

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So this is just a statistics tool
to work out error on repeated values.

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But if we do standard deviation of ‘you’,

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divided by square root of three.

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Because I’ve done three trials,
we get an error 0.041,

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which is fantastic.

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And so yeah, wonderful.

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That is how you work out
G, acceleration due to gravity

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using the PASCO Wireless Smart Gate

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In terms of error
on your experimental method,

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we really want to make sure

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that we’re passing this thing
perfectly straight through here.

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So for example,
if it was to say, for example,

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go through a slight angle
instead of measuring that perfect

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distance here
it might be measuring like the sine

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or cosine of the length

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and that’s going to obviously
alter your reading.

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So something to bare in mind anyway.

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Right.

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Well, thank you very much for watching.
I look forward to seeing you again

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next time
I hope you get really good results.

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Let me know in the comments
and yeah, join us next time.

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Thank you.

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