Materials(hooke's law)

https://5505b400f275fd9f29b9b4679ca512236789cf2e.googledrive.com/host/0B1ZiqBksUHNYZEhDNnU3TUxGaG8/January%202009%20QP%20-%20Unit%202%20AQA%20Physics.pdf

Question 3b


what measurements do i take and what equations can i use to find the mass?

edit: mod close thread pls

Stop

Start reading and understanding the question to think about this systematically.

The clues are already there and will always be in the question.

The first part asks you to state Hookes Law. What is it and what does it mean?

Hookes Law in plain English: The extension of a spring is proportional to the applied force providing it's elastic limit is not exceeded.

It means that a spring (or any material) will increase it's length in a linear manner as a stretching force is applied and will return to it's original length when the force is removed. Wow!

Provided it's elastic limit is not exceeded: i.e. when the stretching force exceeds a limit (governed by the properties of each material), it will not return to it's original length.

Bingo. The clues on how to perform the experiment are all there.

We know that Force = mass x acceleration.

The mass attached to the end of the spring will apply an extension force because of gravity!

Force in Newton's is then simply mass x gravitational acceleration.

The diagram shows a 'standard mass' attached to the spring. The clue is there in the question. Use the standard known mass to calibrate the extension of the spring and plot a straight line graph. This is your reference and you can then use it to take a measurement of the extension for an unknown mass and then use your graph to read off the mass.

So all we need to know is the known precision masses applied to the spring and a method of measuring it's extension and then plot a graph of that force vs extension.

Now you need to think about errors and uncertainty, where they could creep in and how to minimise or eliminate those errors.

You can easily do this. Stop thinking about regurgitating your memory and start thinking about this in a logical systematic way - i.e. how a real physicist would tackle the problem.

eyy i did stating hooke's law ok

i just didn't know what to do for that specific question since although i have done something similar as a practical i didn't understand the rocky bit......

It's all ok now though

Too late i can't not stuff things inside my head, it must be done, it's only the rest of today and tomorrow until i have an exam then i'm doomed

OK.

Then get some good rest and go to bed early to wake refreshed after a good nights sleep. This is incredibly important. It allows your brain to process the information you have already learned/revised. Even though you are not thinking about it, your brain will unconsciously continue to make associations.

Have you never noticed that if you cannot remember a fact (like the answer to a TV quiz that just won't materialise when you need it then and there) the answer pops into your head when you least expect it sometimes hours later or the next day?

Let your brain rest.

You will be better off now only revising things you already know to maximise the marks you can get form doing something well. If you try to learn new stuff at this late stage, you are overstressing and this will affect your performance for the stuff you do know.

Good luck for the exam BTW.

i know i am but i can't afford to let time go to waste ._. i've already wasted too much

And there in that sentence is the reason why you are stressed. I cannot stipulate enough that rest is every bit as important as working.

Do yourself a favour and get some rest.