Question

If, x(t)=0.5(t)-4 where does x=0?

Answer 1

t=8

Answer 2

4/(1/2) =8

Answer 3

makes sense

Answer 4

if x=0, then we are looking for t such that it satisfies
0=.5t-4
add 4 on both sides
4=.5t
2(4)=t
8=t
t=8
so when x=0, t=8

Answer 5

hey myininaya, if you see this reply so I can ask you a more thorough question about this answer. Thanks!

Answer 6

I am about to give up I am so frustrated, mainly because I feel I should know how to do this!

The motion of a train is given by x(t)=.5t-3.5 create a position time graph with accurate slope and intercept. Done already. That was the easy part.



Find the position at 4 seconds. Confirm with an equation

So,
x(4)=0.5(4)-3.5

Solution: -1.5

At what instant is the position zero from the graph? I came up with 7 obviously.

Then it says, from your equation, show your work. Now I am lost, help! lol

Answer 7

for some reason it deleted half my post, what the heck

Answer 8

so we want to know when x=0, what does t=?
x represents the position right?

Answer 9

find the equation of the train given by x(t)=.5t-3.5

Answer 10

right x is the position and t is the time

Answer 11

equation of motion for the train..sorry

Answer 12

so we want to know at what time is the position 0?

Answer 13

using symbols we say:
what does t=? if x=0

Answer 14

yeah, it tells me to find the position at 4 seconds, the confirm with an equation, then at what instant isthe position zero from your graph and then your equation?

Answer 15

well to find when the position is 0
set x=0 and solve for t
so we do
0=.5t-3.5
3.5=.5t
2(3.5)=t
7=t

Answer 16

we want to know know what x=? whent t=4

so we have
x=.5(4)-3.5
x=2-3.5
x=-1.5

Answer 17

agree with that

Answer 18

this second part answers the question:
what is the position when the time is 4 seconds

Answer 19

yeah, i am good on that, its just this, at what instant is the position zero? a) from the graph and b) from your equation.

Answer 20

i think it would be the same?

Answer 21

yes you will get the same answer
unless it is hard to read the graph then you might actually get an approximation looking at the graph

Answer 22

so if the original equation is x(4)=0.5t-3.5 I would just plug in 0 for x (or p) and solve?

Answer 23

what is p?

Answer 24

i am assuming p=position or x axis in this case

Answer 25

lol ok lets assume that

Answer 26

so if you have x(t)=0.5t-3.5
then x(4)=0.5(4)-3.5

Answer 27

which question are you trying to do?

Answer 28

the one about t=4 or the one about x=0?

Answer 29

im gonna scan it in, is that okay?

Answer 30

ok

Answer 31

i almost got it here right now

Answer 32

it just doesn't seem clear o me what it's asking me to do

Answer 33

ok so it looks like you got to e and stop
we want to know what time it is when the position is 0
so we want to what t=? when x=0

so we have the equation that relates position and time:
x(t)=0.5t-3.5
so we just plug in x=0

0=0.5t-3.5
add 3.5 to both sides
3.5=0.5t
multiply 2 on both sides
2(3.5)=t
7=t
t=7

Answer 34

exactly. which is the same thing the graph shows me. so i am assuming they are just wanting me to see the relationship between algebraically and the graph

Answer 35

yes

Answer 36

they are just trying to get you to see you can look at it both ways

Answer 37

i can do the next question by plugging x =12m correct?

Answer 38

12(3.5)=t

Answer 39

42

Answer 40

i didn't get 42

Answer 41

oops, i forgot the .5t

Answer 42

it wont cancel because we aren't looking for position =0 position =12

Answer 43

we have x(t)=.5t-3.5
we want to know what t=? when x=12

12=.5t-3.5

so solve this equation for t

12+3.5=.5t

15.5=.5t
31=t
t=31

Answer 44

first step: add 3.5 on both sides
second step: multiply 2 on both sides

Answer 45

i have no idea why i am making this so hard. I know this stuff. Why am I think stuff like this? ( i know you don't know the answer to that lol)

Answer 46

lol
sometimes you need to take a deep breath and relax for a second and then go back thinking

Answer 47

im actually in calculus and can't do a simpl y=mx+b problem, it's embarassing

Answer 48

i'm teaching cal 2 right now.
don't feel bad you can't do algebra.
it seems most people still struggle with in cal.
i have heard some people said thats where they learned their algebra.

Answer 49

I just bombed my first CALC exam on limits. and I am in phyiscs. its really important to me that I learn my stuff and get my act together. I want to actually succeed. I am ADD so that screws me over really bad, and I am 28. Embarrassing, cause I really want to learn this stuff well.

Answer 50

but you need to work really hard to get caught up
i mean i know you probably are doing this already
you just need to work really really hard and you will get it

Answer 51

I don't want to just "get by" i want to actually be able to see the errors in my own problems too.

Answer 52

oh well, thanks for letting me vent haha. and for all your guidance!

Answer 53

so your teacher knows of your learning disorder?

Answer 54

yes, they all do. However, interestingly enough this hasn't been officially documented. I am going through the testing now, and finish it tomorrow. My Physics Professor caught onto this last year, he has it. My Dr. has always thought I had it, but didn't want to alarm me because I coped so well, until I went back to school that is.

Answer 55

I notice a major difference on medication, and so does my Prof. just waiting to get this official so I can really start to get some guidance to deal with it better

Answer 56

this problem, the one you helped me with. i worked on for 1.5 hours. the sad part is, i do know it too!

Answer 57

my mind wonders, and makes problems harder than they really are. i try to find shortcuts that don't exist, even when I know they don't exist. try to solve problems to fast, have problems thinking slowly through things, ect.

Answer 58

well the only advice i have is to work hard (try to relax your mind and don't let your mind go to many places at once)
but don't forget to take breaks
you can always ask us questions on openstudy.com like you did today

Answer 59

good luck to you!
you can do it!

Answer 60

i just found this site too, thanks for your help and advice!

Answer 61

np
:)