The junior cert science investigations for 2011 were published recently and the phyiscs investigation is as folows:
Investigate the factors that determine the force of friction between a wooden block and the surface on which it is resting.
As usual, there are few spaces for science teachers to discuss how best to implement this investigation so for what it’s worth I’ve decided to throw out my thrupenny worth of ideas and resources.
Why should my students have an advantage over other students who perhaps have a biology specialist as their teacher? Hopefully a Biology/Chemistry teacher will reciprocate with their comments on the other investigations.
Alternatively maybe a student will happen upon this blog post as part of their research – if so good luck to you. Please let us know how you’re getting on and we will try to help.
Some points to consider:
- You would imagine that the orientation of the block would make a difference: if the block is standing on edge then there is less surface-area and presumably less friction. But presumably isn’t good enough in physics; many (maybe even most) relationshiops in physics which were originally thought to be obvious turn out after suitable investigation to be actually wrong. Can you think of any?
To see a demonstration of this see the link here (pull the tab at the bottom over to the 10 minute mark – thanks to colleague Dee Maguire for the link and the heads up on the approach above).
- There is a another nice counterintuitive concept – if students are playing with different types of sandpaper they may well find that the friction force between the wooden block and the roughest type of sandpaper is actually less than the force of friction between the wooden block and the lab-bench.
Hopefully the students will first notice this stange relationship and then figure out why for themselves (this should then form part of their report. Partial explanation – the grains in the very rough sandpaper are acutally acting like little ball-bearings (see link below for an animation).
- Simulations for friction on an microscopic level:
It includes links to simulations of the following:
- Friction between two rough surfaces from absorblearning.com
- Friction between two rough surfaces
- The effect of ball-bearings in reducing friction
- The effect of lubrication in reducing friction
- Rub the two books against each other and note the rise in temperature
Do you have any idea what the equation between the friction and gravity is?
The friction force divided by the weight (for a object being pulled horizontally) is equal to a constant for those two surfaces.
The equation would be Friction force = u R, where R is the reaction force which for horizontal movement is the the same as the weight.
u is called the coefficient of friction (acually latin letter, pronounced “meu”).
Google ‘coefficient of friction’ for more, or ask your teacher for an old physics textbook.
And good luck – you’re off to a good start.
Thank you. 😀
what are you going using that in ?
i am confused could someone please help much appreciated
what would the variables be in this experiment?
things like the surface it is placed on, the mass and the pressure put on the wooden block..
im doing the junior cert physics investigation and im wondering what do they want us to research.i know they want us to research the experiment but research what about it?
has your teacher not given u a practice project sheet?
you guys wer rele helpful thank you!
what do you guys think i should say for my method?
hi , i was just wondering that if i had a ramp of some sort in my experiment , what should i make it from ? i thought a bout using a small piece of perspex but i thought it would scratch easily ! please reply because i am in need of some advice!
well the whole point is you use a variety of surfaces so that you can get good results
what would you fill into the space for ” particular safety precautions required by this investigation” ?
Hi, I’m currently starting this investigation for the Junior Cert. I’m a bit confused about what a variable is, especially regarding to this experiment. Any help, please? Thanks 🙂
this is very helpful! just try the links
Can obscene comments on this page be deleted? I would like to be able to recommend this resource but can’t as is.
Im just wandering do you use a spring balance or is there another way to measure the friction because my teacher is using weights and a long piece of string but i don’t know how this works?
my teacher keeps giving out to me for my conclusion being rubish what sort of thing should i say for it?
hi so confused on de physics investigation!:( our teacher tels us notin ATAL bout it! ne idea on wat way 2 do it ? i’m in bad need of help, much appreciated 🙂