lacoste's PHYSICS questions

[lacoste]

51.34 degrees is equal to 51degrees20seconds.

do i place my final answer as which one of the above?

[Collin Li]

direction is S53degrees20secondsE? book got different.

51.34 degrees is equal to 51degrees20seconds.

You wrote 53 in the first post so I thought you did a rounding error or something. Also, it should be 20 minutes, not seconds.

Yeah, they're all the same. I think Physics would prefer decimal places (rather than degrees, minutes, seconds)

[lacoste]

oh yes, opps about the minutes and seconds mistake.

big thanks for the clear-up!!

[lacoste]

how did you get S51.34E?
its driving me nuts!!
the book got the same S51.3E; but when do you drop the four?

They're probably just stating it to 1 decimal place, rather than 2. It's the same answer (me and the book)

You probably got 53 by using your rounded off values or something like that.

What I did was solve (to 2 d.p.)

shouldn't you solve (to 2 d.p.)
then, do 90-38.66=51.34 ?

is it possible for a diagram using latex?
     100km
   ----->
   \      |
     \    | 
       \  | 80km
          V


[then a diagonal line connecting from top left corner to bottom right corner]
use tan. opposite is 80km, adjacent is 100km?


or did you work it out a different way coblin?

       
 

[Collin Li]

You can do it that way as well. I drew the southward vector first, then the eastward vector, so I got a triangle on the lower-left hand side (yours is upper-right hand side).

Code: [Select]

      upper-right
    ___
   |\  |
   | \ |
   |__\|
   
lower-left
Then I used the angle up the top, so that the opposite was 100 and the adjacent was 80, which would directly give me the angle which fits in between SE.

[lacoste]

thanks mate.

 another question...does significant figures in chemistry and physics differ? if so can you please explain?

[Collin Li]

No. You'll even see "significant figures" in Specialist Maths!

Same meaning. Only difference is that Chemistry cares about it and Physics doesn't really care about it (which is why I arbitrarily chose 2 decimal places).

[lacoste]

Do we have to memorize the Linear Motion formulas? They are given to use on a data booklet but will it be of benefit to memorize ALL or some of those formulas? 
eg. v=u+at

Is there a method to quickly remember these?

[/0]

Do we have to memorize the Linear Motion formulas? They are given to use on a data booklet but will it be of benefit to memorize ALL or some of those formulas? 
eg. v=u+at

Is there a method to quickly remember these?

There are only 5 of them, and they aren't that hard... you should definitely memorize them.

(could be intuitive... I guess, just think about it)

(you could rote learn, or realise this is the antiderivative of the first equation)

(If you know the second equation, this should follow quickly)

(This can be derived from a v-t graph, and that may help you memorize)

(just memorize it lol)

[lacoste]

cheers /0! i can derive some but i guess rote learn is better, because i wont have time deriving during exam time.

How do I work out the instantaneous speed of a question? without a graph
[is there a quick method?] btw, the book doesn't even have that in an example

[Flaming_Arrow]

well just say a questions says a car is traveling at and its acceleration is and they ask you to find the velocity at the 7th second

so u = 10  a= 5   t = 7

then just use the equation from there

[lacoste]

I have trouble with significant figures in physics. If it doesn't state then what happens?

Can somebody shed some light?

[Flaming_Arrow]

what do u mean?

[NE2000]

I have trouble with significant figures in physics. If it doesn't state then what happens?

Can somebody shed some light?

Typically in chemistry you would just go with the lowest number of significant figures present in the question, as it would be inaccurate to present your answers to any higher a level of significant figures. The same generally holds true for physics and any other subject for that matter, only they tend to be more lenient in physics.

So if the question gave you 10.3 m/s, 5.1 m/s/s and 3.45 seconds as your given value, your answer would be to 2 significant figures (like the acceleration value).

[/0]

Do you think it would be safe in physics to 'generally' put your answer to 2 decimal places?