how many sf in phys??? (1 Viewer)

[neuvie]

in any physics question, where the answer has a lot of decimal points and/or is irrational, how many sf do you write it in?? ive been told that you "answer in the least amt of sig fig that you used in calculation" but i dont get what that means. additionally, this is in terms of both working out steps in between (ie, calculating velocity and then using that value to get the acceleration, etc) as well as final answer.

i do matrix online tutoring for physics and have been going back to try the workbook, however my answer is wrong by +/- around 0.1 because im putting in the exact value that i got in calculation, whereas they round it to a certain amount of decimal places which is different every time and its so confusing. for example, the vertical velocity is 15sin60 but then sometimes they might round it to 12.99, or 13.0 and it always keeps changing i just dont get it.

youre welcome to ask me to clarify my question, or to provide more examples on what i mean, thank you for your replies!

 

[wollongong warrior]

Use variables in your calculations, plug numbers in at the end, answer with the same amount of sig figs as the question or 2 decimal places if unspecified

 

[neuvie]

Use variables in your calculations, plug numbers in at the end, answer with the same amount of sig figs as the question or 2 decimal places if unspecified

what do you mean by variables in calculation? also at the end when you say sig fig in the question, is it according to the lowest or highest amt of sig fig?

 

[english? ensquish]

in the question you get given numerical data right? what's the lowest amount of sig figs in the data you get given? from that number, write your answer in the same amount of sig figs

hope that helps

 

[english? ensquish]

use the 'actual' value from your calculator during your calculations though. only round to the required sig fig at the end for accuracy

 

[liamkk112]

what do you mean by variables in calculation? also at the end when you say sig fig in the question, is it according to the lowest or highest amt of sig fig?

according to the lowest amount

when they said variables in calculation, they meant don’t plug in numbers straight away and keep it until the end. eg say you have the formula λ=h/mv, and you want to know the frequency of the wave, don’t plug in h, m and v into that equation, instead write f = v/λ = mv^2/h and then plug in all of the numbers there; that ensures you don’t carry any rounding errors in the question

 

[neuvie]

use the 'actual' value from your calculator during your calculations though. only round to the required sig fig at the end for accuracy

thank you very much for the clarification (again)

 

[neuvie]

according to the lowest amount

when they said variables in calculation, they meant don’t plug in numbers straight away and keep it until the end. eg say you have the formula λ=h/mv, and you want to know the frequency of the wave, don’t plug in h, m and v into that equation, instead write f = v/λ = mv^2/h and then plug in all of the numbers there; that ensures you don’t carry any rounding errors in the question

thank you very much for the clarification

 

[neuvie]

use the 'actual' value from your calculator during your calculations though. only round to the required sig fig at the end for accuracy

sorry but just another question, when i use the actual value should i write "..."? for example 1.23456789 as 1.23... or just 1.23

 

[liamkk112]

sorry but just another question, when i use the actual value should i write "..."? for example 1.23456789 as 1.23... or just 1.23

i would write 1.23... = 1.23 (3sf) or just 1.23 (3sf)

 

[neuvie]

i would write 1.23... = 1.23 (3sf) or just 1.23 (3sf)

that is for the steps in between as well, right?
for example finding v from v=u+at and then finding p from p=mv (just example)
like v=1.23 (3sf) and then p=mv=m(1.23) etc, or v=1.23... and then p=m(1.23...)
sorry it sounds so dumb but i just dont get the hang of it

 

[wollongong warrior]

that is for the steps in between as well, right?
for example finding v from v=u+at and then finding p from p=mv (just example)
like v=1.23 (3sf) and then p=mv=m(1.23) etc, or v=1.23... and then p=m(1.23...)
sorry it sounds so dumb but i just dont get the hang of it

p=m(1.23...)

 

[wollongong warrior]

If you round your numbers within your calculations, rounding errors will start adding up and your final calculation would differ from the answer

 

[neuvie]

p=m(1.23...)

thank you so much again for the answer
i think i get it now