hi , i am having a lot of trouble with this problem any help would be appreciated A little cat, Bella, walks in a straight line, which we shall call the x axis, with the positive direction to the right. As an observant scientist, you make measurements of her motion and construct a graph of the little feline's velocity as a function of time. Find the x component of Bella's velocity at t = 4.00 s. give me a sec have to draw graph...

- anonymous

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- anonymous

to see the graph i found the question online here it is http://www.cobaltss.net/forums/lounge-42/anyone-good-physics-151699/

- anonymous

\[v(t)=\frac{-4}{3}t+8\]

- anonymous

\[a(t)=\frac{-4}3{}\]

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## More answers

- anonymous

a) t=4
v(t)=-16/3+8
v(t=4)=2.66

- anonymous

can you please explain to me what the question is asking

- anonymous

i mean how did you figure out the first equation you wrote

- anonymous

ok, the line is passing (0,8) and (6,0) right

- anonymous

yah

- anonymous

and we know its slope is -8/6

- anonymous

yah

- anonymous

y=mx+n
its formula

- anonymous

okay

- anonymous

put m=-8/6
and (0,8) or (6,0) to find n

- anonymous

y=-8/6x+8=-4/3+8

- anonymous

y=V(t)
x=t

- anonymous

so this is how find the velocity

- anonymous

|dw:1328511634338:dw|

- anonymous

and now you have v(t) so you can find v at any time

- anonymous

yah

- anonymous

do you know derivative

- anonymous

kinda of

- anonymous

this cat is negative accelating (deceleration ) and t=6 v=0 it means at t=6 it stops in a short time and going to opposite side(speed up)..

- anonymous

dx/dt=v(t)
dv/dt=a(t)

- anonymous

that`s how I found a(t)

- anonymous

ehats a(t)

- anonymous

ehats?

- anonymous

i means whats a(t)

- anonymous

acceleration at t = 6.00 s.

- anonymous

you need it for question c,d,e

- anonymous

what is the difference between velocity and acceleration

- anonymous

In physics, acceleration is the rate of change of velocity with time

- anonymous

acceleration is always constant or zero

- anonymous

if velocity is constant then a is zero

- anonymous

in your question, v is not constant, it changes with time, so there is an accelation

- anonymous

|dw:1328512464896:dw|

- anonymous

|dw:1328512506539:dw|

- anonymous

so if velocity is constant acceleration is zero if not it changes

- anonymous

was i suppose to use this equation for this problem

##### 1 Attachment

- anonymous

so if velocity is constant acceleration is zero that's right

- anonymous

can u take a look at the formula i attached

- anonymous

you can use it.
you know that a is constant and it is -4/3 already
v0=8
v(x) we looking for at t=?

- anonymous

sryy how do you know acceleration constant

- anonymous

because a is slope of v, v is a line, slope doesnot change in time, it is constant

- anonymous

as I said before a is zero or constant ALWAYS

- anonymous

|dw:1328513106159:dw|

- anonymous

how do you know if it is zero or constant

- anonymous

take a look graph which I drew at up..

- anonymous

its constant

- anonymous

ok, there is always two stuation,

- anonymous

|dw:1328513296298:dw|

- anonymous

this one is first stuation..

- anonymous

the velocity is increasing then decreasing

- anonymous

velocity is not constant

- anonymous

yah

- anonymous

|dw:1328513379149:dw|

- anonymous

this is secend stuation, v is constant

- anonymous

yah

- anonymous

your problem is first one..

- anonymous

yah . the last graph you drew show that velocity is zero

- anonymous

but I drew speed up, yours is speed down

- anonymous

yah i can see that

- anonymous

and it has inital velocity which is 8

- anonymous

so everything is clear now

- anonymous

so you said acceler is alway zero or constant is velocity is constant its zero. what if velocity is zero

- anonymous

it means that car remains stop, no act no acce..

- anonymous

and if acceleration is zero what does that tell you about your car

- anonymous

if you are driving a car 50 mile/h all the way then your accel is 0
if you are speeding 50 to 100 in 1 min then there is accele. which is const..

- anonymous

your car is stop

- anonymous

i apologize for making you repeat but if you have constant velocity , then the acceleration of your car would be...

- anonymous

http://wiki.answers.com/Q/What_causes_acceleration_to_increase

- anonymous

0

- anonymous

|dw:1328514179090:dw|

- anonymous

constant velocity

- anonymous

v doesnt change with time, so a is zero

- anonymous

so the car is stopped?

- anonymous

because acceleration is zero

- anonymous

no, acceleration is zero doesnot require v is zero, v can be zero or constant, either way a is zero

- anonymous

okay got it thank you

- anonymous

can you give me some help with the next part

- anonymous

I need it see it, I cant promise..

- anonymous

so if i need to find x component of her acceleration at t = 4.00 s.

- anonymous

i know that her acceleration is constant

- anonymous

yes, her a is always -4/3 constant
you see a(t)=-4/3 doesnot depent on t

- anonymous

so whatever you plug into t, it will always will be -4/3

- anonymous

yes.. but for accel right

- anonymous

i mean whatever you plug in for t into the equation: y=-4/3t+8

- anonymous

y=-4/3t+8 this eq. is for finding v at some certain time
v(t)=-4/3t+8
a and b you need to use this eq.
a(t)=-4/3
c,d,e use this formula

- anonymous

i dont know what to do

- anonymous

a) t=4 v=(-4/3)*4+8=2.66 is that right

- anonymous

yah

- anonymous

or
v=v0+at
v=8-(4/3)*4

- anonymous

solve the same way t=7

- anonymous

ill be back in ahour my battey is low

- anonymous

ok..

- anonymous

maybe I can't stay that long..

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