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Physics homework ! online mentor required!URgent

hey guys i wanted to create a thread where all the physics geniuses come out to play!
i am not one of them , i happen too have picked it as it will help in a career involving engineering and will be studying it, both my teachers are good in the sense that they try to explain but they cannot explain it at all , i get hw on things that i am completely lost about! and they do a poor job of explaining it in the first place, theyn give us paper with answers no explanation and now they have begun to hand us hw form a random book so please ppl , i know u guys are supersmart please help me , i am in need of your assistance!!!!!!!!!!

here is my hw for this weekend; how to do it? i have no idea! :confused:

Reply 1

Dhampir

What part are you stuck with?

Reply 2

ankur29

ques 2 onwards , i did 1 but not sure bout ma ans? it say "horizontal velocity small/large air resistance

bout ques 2, it says calculate time we knw due to g accelaration is 9.81m/s(2) but wahat is the speed , same kidn of thing for 11.3 and i am so confused!!!!!!!!!!

Reply 3

Dhampir

You need to use the equations of linear motion.

v=u+at

s=ut+0.5 a*t^2

v^2 = u^2 +2as

Reply 4

ankur29

whic 1 do i use?what about the others

Reply 5

Dhampir

You need to use the equation with the correct variables to match what you know.
For the second question, you know the inital speed (u) the acceleration (a) and the distance (s), and you need to find the time (t), so you have to use the equation s = ut + 0.5a*t^2.

Reply 6

ankur29

is the ans to 11.2 0.19s?

Reply 7

Dhampir

no. you haven't done the right thing with the half

Reply 8

ankur29

ok i changed it n got 0.42?

yep.

is the ans the same 4 11.3? and is teh speed 15.24m/s

Reply 11

anderue

ankur29

ok i changed it n got 0.42?

That's correct (to 2s.f.).

Do you not have a textbook you could learn from?

Reply 12

ankur29

unfortunely i need examples of quest to laern 4rm and teh horizontal n vertical stuf was confusin me

Reply 13

ankur29

how do i do 10.4 & 5?

Reply 14

Henerz

ankur29

how do i do 10.4 & 5?

You mean 11.4 & 5?

11.4

Horizontal and vertical motion are independant of one another, so you consider the motion vertically and horizontally separately. Recognize that from your physics lessons?

So, I put a line down the middle of my page and on the left hand side title it vertically and on the right-hand side title it horizontally. Now I write down everything I know about each direction of motion.

Vertically:

1) What is acceleration,a? The bullet is in free fall.
2) What is displacment,s?
3) What is the inital vertical velocity?
4) What is the quantity you are trying to find?
5) Which formula (Dhampir posted all the ones you'll ever need for this type of question) links the 3 known quantities and the forth unknown?

Put what you know into the selected formula and solve for the unknown.

The time taken for this vertiacal motion to happen will always be the same as the time taken for the horizontal stuff to happen...that stands to reason as the begin and end at the same time?

So, you can find out the time for the horizontal motion, and you might just have 3 quantites necessary to use a formula to find something else out :smile:

Reply 15

ankur29

thanks for all the help!everyone, ma teacher had to explain it to all teh class so i understood it now my new fear in physics in physics right now is velocity timegraphs and displacement graphs how do i undertsand them! here are the ques i have been given

it is teh attached file, have a look at Q9

velocity exam q.doc34.3KB

Reply 16

Wangers

Post your efforts first, we are glad to help, but not to be a homework service.

Reply 17

ankur29

for teh first bit of 9 i wrote 2(s) for teh instant it hits teh ground teh third time but i dnt knw how to get 2 marks?i am not sure what it is askin?what the scale is? etc.........

i wrote for the second bit that teh sloping line is straight beacuse the accelaeration due to gravity(hence teh negative slope) is constant

and f or teh third one do we use suvat in terms of vertical motion and calculate 's'(displacement) if so what is teh intial and final velocity?

etc i am so confused about thsi hw, i was not fully taught this!