physics dotpoint (1 Viewer)

[:: ck ::]

perform an investigation and gather information to determine a value for acceleration due to gravity using pendulum motion or computer-assisted technology and identify reasons for the possible variations from the value 9.8 ms^-2

mmm wot i need to know are some reasons for the possible variations from the value of 9.8ms^-2

all i can think is... measuring inaccuracies - length of string / timer for 10 oscillations not done properly... environment was not suitable (like doing it next to a window)

ermz.. the experiment was done at a high altitude?

mm wot can i write for the reasons part =\

 

[:: ck ::]

hmm also wots the point of finding the gradient when graphing T² vs Length

is there a point to it 0.o and how does it relate to giving u the value of g ..~

 

[Suvat]

Experimental errors, variations in the distance from the centre of the Earth, variations in crust composition e.g. high density metallic ore bodies underground increase the value of g while salt domes decrease the value, the movement of tides (negligible)

the gradient of T^2 against l is equal to 4pi^2/g, which then can be rearranged to find g. we prolly use T^2 and l because those values were the easiest to obtain from our measurements

 

[:: ck ::]

mm i know wot the gradient is but really, theres no point in finding the gradient is there??

using the formula T = 2pisqrt(L/g) u can easily arrange it to find g without having to calculate the gradient of the graph T^2 vs Length

hrmmz.....

 

[Constip8edSkunk]

the reason you use the gradient is that it provides a better estimate.

also, note that the formula does not give an exact value for g, only an approximation assuming the angle @ -> 0.

 

[Suvat]

Have you got icq John?

 

[Constip8edSkunk]

PM

 

[Xayma]

Originally posted by :: ryan.cck ::
mm i know wot the gradient is but really, theres no point in finding the gradient is there??

using the formula T = 2pisqrt(L/g) u can easily arrange it to find g without having to calculate the gradient of the graph T^2 vs Length

hrmmz.....

The gradient should be the line of best fits gradient, there really is no difference between that and picking a point off the line of best fit.

 

[:: ck ::]

0.o so the gradient is just to prove its a linear relationship between T² and Length.. hrmz..

bleh stuff it im goin crazy over something so little..

 

[Xayma]

Originally posted by :: ryan.cck ::
0.o so the gradient is just to prove its a linear relationship between T² and Length.. hrmz..

Basically, since you have to draw a line of best fit if you have to graph it, you may as well pick a point off it.

 

[Constip8edSkunk]

but when calculating the gradient, you use the furtherest pt of the graph and calculation of this pt is more accurate than any other points closer to the origin (as they are more prone to errors in the measuring and calculation process)

 

[Suvat]

I hate graphs
got robbed of a mark in a physics pract for not drawing an arrow pointing to the line of best fit with LOBF on the other end...

 

[zeropoint]

Originally posted by :: ryan.cck ::
hmm also wots the point of finding the gradient when graphing T² vs Length

is there a point to it 0.o and how does it relate to giving u the value of g ..~

The principle reason to graph T² versus L (or preferably T versus L^1/2) rather than average the results is to minimise the impact of bad data on the overall result. In principle, a straight line regression will place less emphasis on data that is more distant from the line of best fit, as compared to an average which places equal emphasis on all data points. Furthermore, graphical inspection allows the experimenter to ignore data points that are deemed erroneous when computing the slope of the curve. The numerical result of slope of the curve can be substituted for T²/L in the following expression to obtain an estimation of g = (4pi²)/(T²/L).