A-level Physics Core Practical: Finding a value for g using a free fall method

Notes to accompany this film are posted here: nustem.uk/activity/measuring-g/
Alom Shaha presents several approaches to the classic practical, which as of September 2015 is a required part of A-level Physics study. With Christina Astin and Ronan McDonald he discusses the pros and cons of four methods, covering the strengths and weaknesses of each and how they might affect your approach in the school lab.
Presented & Produced by Alom Shaha.
Directed & Edited by Jonathan Sanderson
Advisors: Christina Astine & Ronan McDonald
With thanks to: David Sang, Dr. Carol Davenport, Alex Cummings, Ken Zetie.
Music by Kevin MacLeod, incompetech.com
Produced by Physics Partners and Think Physics, with assistance from Watford UTC and the Ogden Trust.
** 4th Feb 2016: Now with corrected subtitles! **

[@juliahicksfav]

When he switched places with the professor to let her perform the experiment. This guy is wholesome af.

[@robertserram9219]

He's a beta, pretty sure her wife has some boyfriends.

[@artemisl3506]

@@robertserram9219 ??????????? Right...

[@STAA.R05]

@@robertserram9219how do you know?

[@PhysicsOnline]

That's a fantastically well produced video. Are you planning to cover all the core practicals for the practical endorsement?

[@JonathanSanderson]

+A Level Physics Online Short answer: yes, that's the plan. We're seeking funding support for the full set, but it looks like we've enough to at least make a start. Thanks for your kind words!

[@PhysicsOnline]

+Jonathan Sanderson Will they be aimed at teachers or for the students?

[@JonathanSanderson]

+A Level Physics Online As with our previous films, they're aimed primarily at teachers. That said, many teachers report using them with their students, often for revision purposes.

[@janetseymour6270]

These videos are a great resource for the A 2 students in preparation for the exam. Thank you

[@Valkriecain99]

Aw I liked this. I did the gravity experiment a couple of days ago and was researching general physics resources when I found this. Very good points that teachers fail to share-not because they're incompetent, but because students are meant to be doing practicals with minimal support. So this is quite useful for students, and I will be checking back during my next practical to see if I can get any more guidance. I quite liked the friendly laid back atmosphere of the video. Thanks!

[@othcortes1715]

The last one which used magnet switch and a mechanical switch at the bottom, in my own opinion, can give precise signal to the timer. Great work of physics to share with.

[@awolgeordie9926]

Excellent. Just did this in class today. Manually. I teach CIE A Level Maths and Physics in Thailand but originally hail from Geordieland.

[@jenniferwilson5379]

i really enjoyed this and found it easy to learn from. Plus very wholesome makes me love physics all over again

[@melodykamil]

That was so helpful. Thank you very much!

[@DennisChangweKunda]

Brilliance at the core

[@beigeboi_7714]

Thank you, Alom

[@mukongtangwa2984]

So cool. I had a lot of fun watching that

[@user-pb6rn1xk4b]

very good video thank you

[@richardneedham9345]

As you point out, dropping a ball through two light gates is not a perfect method for this investigation. 'Better' data can be collected by using a rectangular object rather than a sphere, to ensure the light beam is interrupted by the same point on the falling object. A transparent ruler with a strip of black insulation tape makes a good interrupt card. When using light gates it is more economical, and it speeds up the activity, if a single light gate is used with a double interrupt card (such as a transparent ruler with two strips of black tape). Most data logging manufacturers sell proprietary interrupt cards, although these may have other names such as a 'picket fence'.

[@stustjohn]

Great video. Impressed that you got Daniel Craig to present the electromagnet/trap-door switch part! ;-)

[@Syiepherze]

Are you sure that wasn't Putin?

[@MohammadSalman-zq2rv]

the best video ever

[@fawazsm]

great video ... and by the way those were hell of a quick mental calculations !!! ;P

[@vg6761]

The y-axis variable can even be 2s, that way the gradient will = g without later multiplying it by 2.

[@dartplayer170]

The correct explanation of why to use the g-ball is that it is more consistent and eliminates human systematic errors in reaction time of manually using a stopwatch. The measurement error is virtually the same. This technique can give about 0.3m/s2 error on 1 measurement which is confirmed by the example here 0f 9.6m/s2. Better results could be attained with a millisecond timer giving 3 significant figures as the error in height is not really contributing to the total error with a 1/100s clock.

[@nishikantprasad7825]

Incline plane method could also be a way to extract g

[@gkpgeo]

Can we use for measuring for accuracy of 10 micro gals resolution?

[@ch.usmanzafar3648]

best video

[@SkyDarmos]

The freefall acceleration depends on the chemical composition. So they can do real research if they measure precise enough and use different materials.

[@Ethanjg]

This is an awesome video. When will another video be released?

[@JonathanSanderson]

We've recently recorded three more films in this series, but it's hard to say when they'll appear; they need to be edited, then signed off by everyone involved. So: a few weeks.

[@Ethanjg]

+Jonathan Sanderson Awesome, that's good to hear :)

[@MyNameIsShobzy]

Why isn't there this for bio + chem :(

[@NUSTEM]

We (Alom and I) have made a series of films in this style over the last few years. Most of them are physics, but a few were biology and chemistry. The ones which are publicly-available are here: nustem.uk/activity/a-level-physics-required-practicals/, and we continue to push for the remaining films to be published on KZbin - they're currently trapped at the National STEM Centre website and a few other place. Unfortunately, we don't have complete control over all the films.

[@SkyDarmos]

A robotic release mechanism should be the best choice. I hope I can find that somewhere.

[@gideonboulton]

At 5.16, it would have been great to see some error bars, and look at the range of values of g you could get - but I suppose you have have a limited amount of time really. Great initiative though.

[@carultch]

I was able to get g=9.77m/s^2 with the g-ball, when the accepted value at my location is 9.803 m/s^2, using half meter intervals up to 4 meters. My closest data point to the accepted value came with a drop height of 2 meters. To high, and air drag becomes significant. Too low, and the resolution of the timer can't get enough precision.

[@MohammadSalman-zq2rv]

sir i dont know how u decide the y axis the x axis and the gradient by rearranging equations like the one u did where s was on y axis and t^2 on the x axis and then gradient aswell.Plz make a video teaching how we can do this.

[@asifmahmoud126]

I have the same problem

[@arrushc7029]

If you re-arrange the equation s = ut + 1/2 at^2 to find for a or you can say g, the x-axis and y-axis would produce the same output: s = ut + 1/2 at^2 s - ut = 1/2 at^2 2s - 2ut = at^2 2s = at^2 + 2ut 2s = t (at + 2u) 2s / t = at + 2u Hope this helps :)

[@arrushc7029]

Furthermore, this has to be graphically similar to the equation of a line: y= mx + c. In this case it does hence the equation in the video is correct

[@gowridharshini7010]

May I please know why where the heights not considered as negative values? since the drop is a negative direction?

[@carultch]

It is arbitrary what direction we consider to be positive vs negative. Since g is positive unless context and coordinate system requires otherwise, then if it is my choice, I would assign downward as positive, and y-position final as zero, and each of the initial positions as y0 in y = y0 + v0*t + 1/2*g*t^2.

[@mr.ahmedjama2589]

Pushin P my guy

[@SkyDarmos]

The problem with a magnetic release mechanism is that it only works for balls that are magnetic. Iron and steel are magnetic, but most metals are not magnetic.

[@saketpanigrahi]

You cn measure g by the help of formula T=2(PI) (L÷g)^1÷2. You need a thread and a (mass) object. In zero budget. I get 9.9 by this techmique but you can measure it more precisely

[@NUSTEM]

Ah, I remember doing that as my first practical lab at university…. :-) More importantly, we have a film about this, too: kzbin.info/www/bejne/h3azZIqDobZ5o80

[@carultch]

@@NUSTEM Would Atwood's machine qualify for teaching an experimental way to determine g, for the A-level program? That was a historical method, where he used pulleys and counterweights to slow down the kinematics, to reduce the impact of reaction time.

[@ibraheembaloch9772]

what is that ball called ?/???//

[@JonathanSanderson]

Notes to go with the film are posted here: nustem.uk/activity/measuring-g/ …which I hope will answer your question.

[@ibraheembaloch9772]

can you tell me about an experiment to calculate young modulus

[@lucabarnes9844]

yo

[@markkeown9532]

More data dose not mean that you will get closer to the correct value. Attention to detail will. Now is the height value that you are using - the ruler value less the diameter of the ball? And 0, 0 is a good data point why not use it.

[@SkyDarmos]

Taking the average is a completely wrong approach for this type of experiment.

[@robertserram9219]

3:58 BETA male