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

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.

Produced by Physics Partners and Think Physics, with assistance from Watford UTC and the Ogden Trust.

** 4th Feb 2016: Now with corrected subtitles! **

[GTChow]

Best video on this practical on the internet hands-down. Great work!

[juliahicksfav]

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

[PhysicsOnline]

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

[janetseymour]

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

[othcortes]

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.

[Valkriecain]

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!

[stustjohn]

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

[awolgeordie]

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

[jenniferwilson]

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

[richardneedham]

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'.

[melodykamil]

That was so helpful. Thank you very much!

[dartplayer]

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.

[fawazsm]

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

[vg]

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

[nishikantprasad]

Incline plane method could also be a way to extract g

[mukongtangwa]

So cool. I had a lot of fun watching that

[SkyDarmos]

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

[MohammadSalman-zqrv]

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.

[MyNameIsShobzy]

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

[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