Physics Question

[onur369]

Hey guys Im stuck on the the following questions:



Following questions:

- How long was the basketball in the air as it travelled from A to B?  I think I did this correct someone confirm please,
t= root2h/g 
root 0.4
= 0.63
The one below is the one I couldnt do
- What is the height, y, of the hoop above the ground?

[xZero]

for the first question i got t=0.622s

now for the second question,
x=ut+0.5at^2, where
t=0.622s
a=-9.8ms^-2
u=7.5sin(50)

plug all the numbers in and you'll get x, however you have to add 2m to it since the basketball player launched it at 2m height

[onur369]

Thanks mate, how did u approach the first question?

[xZero]

v=7.5cos(50)
x=ut, where u = v, x=3 and solve for t

[schnappy]

v_x = 7.5cos(50)
d = 3m, v=d/t

For the second part, you know t, a=g=-10.
x=ut + 0.5gtt +x_0
u=7.5sin(50), t=(as per q1), 0.5=0.5 (oh snap), g=-10, x_0 = 2.

[onur369]

Thanks guys, also hows VCAA with the decimal place system, I got 0.63 for the first question but you guys got 0.62, do they mark me down for things like that?

[xZero]

yes they do, but if you use 0.63 for the next answer they should give you consequential marks. For physics its usually round up to 3 significant places.

[schnappy]

afaik they're not that picky. Not like in chem, urgh.

yes they do, but if you use 0.63 for the next answer they should give you consequential marks. For physics its usually round up to 3 significant places.

3 significant places eh? Sounds like someone doesn't understand sig figs.

[onur369]

this is vcaa we are talking about, theyre pricks so I guess I should just be on the safe side.

[xZero]

afaik they're not that picky. Not like in chem, urgh.

yes they do, but if you use 0.63 for the next answer they should give you consequential marks. For physics its usually round up to 3 significant places.

3 significant places eh? Sounds like someone doesn't understand sig figs.

rofl you're right apparently you learn sig figs in chem but I never did it well according to my teacher and tutor, 3 sig figs are required in the exam.

Also VCAA will take the mark off for using 0.63 instead of 0.62 since there weren't any ambiguous variable involved i.e. gravity is 10ms^-2 in physics but you can also use 9.8ms^-2

[onur369]

Thats quite harsh 0.01 difference

[xZero]

Even though its a tiny difference, the correct rounding off is 0.62 not 0.63, so I don't see why VCAA won't take the mark off. Remember we're dealing with VCAA so its better to be save then sorry.

[golden]

In that case why did I lose marks on my SAC for having too many decimal places even though it was in 2 significant figures all up? It was like 0.000##.

[xZero]

Did the question required you to round the answer off? I don't see how you can loss a mark for being too accurate

[golden]

It's the one about Luna Park where we have to write a report - I included the error cutoff in the answer with regard to the kinetic and potential energy:

Answer +-(% error)x(answer) which came out to be answer +- 0.000## or something (I used two significant figures which was consistent with the actual answer itself).


In the criteria it said to use an appropriate number of significant figures.

In Chemistry significant figures don't include the leading zeros eg. 0.000... but include the trailing zeros eg. 1.000.

In Physics this should be the same right? Or is it decimal place based?