velocity time graph

[plush kernel]

1. is the acceleration for the whole graph same?
2. how to calculate acceleration after 2seconds, for first 2 sec ik its 5 m/s^2

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[austere notch]

What is acceleration?

[plush kernel]

change in velocity/change in time

[austere notch]

Yes change in velocity w.r.t to time

So in the graph what represents change in velocity wrt to time

[plush kernel]

the slope of the graph

[austere notch]

Yes

[plush kernel]

but its changes 3 times

[austere notch]

2 times

[plush kernel]

is it same for all?

[plush kernel]

oh yes

[austere notch]

There are 2 slopes

[austere notch]

Wdym by same for all?

[plush kernel]

the slope must be same before and after 2 seconds, aint it?

in this graph

[austere notch]

Why?

[plush kernel]

cuz it looks like that, time is 2 seconds when the velocity is 0

idk

[austere notch]

Do you mean the magnitude of acceleration?

[plush kernel]

sorry whatever i said doesnt make sense to me

i dont understand it , is it just bcz of geometry

[austere notch]

The magnitude of acceleration is the same but diffrent directions

[plush kernel]

that why i thought slope looks alike

[austere notch]

The slope is defined as tan(angle from +ve x axis) both slopes are same in magnitude opposite in signs

[plush kernel]

ohk, for the first 2 sec its accelerating, for the next 2sec is decelerating, and after 4th sec too its decelerating?

[austere notch]

Yes

That's why it gets back to zero after 2sec

[plush kernel]

yep

[austere notch]

For first 2 seconds a=5m/s^2 and after 2sec it's -5m/s^2

[plush kernel]

now while calculating the displacement , this guy used the acceleration =5m/s^2 , which is for the first 2 seconds, so im confused why he used 5 , to make the area of 2 triangles equal, which would make our displacement equal, which wud get me the time when the displacement is =0

triangles area gives the displacement in vt graph

thats what i know

[austere notch]

Any area gives displacement under vt graph

Not just triangles

[plush kernel]

yeah ik

thanq

[austere notch]

So for first 4 sec displacement is 20m

[plush kernel]

but the qs

[plush kernel]

yes

[austere notch]

So you'd need -20 area to make it zero

Meaning 20 area under x axis

Find how big of a right triangle you'd need for that

[plush kernel]

yeah getting it, but how to put values in suvat

[austere notch]

Suvat?

[plush kernel]

s= ut+ 1/2at^2

[austere notch]

Ah

s = 0 you need but you can't put it

[plush kernel]

what do i put in 's'

[plush kernel]

ok

[austere notch]

Acceleration is not constant you'd have to use it 2 times

You cant directly put s=0

@plush kernel

[plush kernel]

yes'

ok

[austere notch]

I'd suggest doing it by graph instead

[plush kernel]

first its 5m/s2 then its -5m/s2

[plush kernel]

how

[austere notch]

You have +20 area how much do you have to extend the line to make a triangle with -20 area?

-ve meaning below x axis

[plush kernel]

exact copy of the positive side

i never knew the length of the line

[austere notch]

No you can't change the acceleration

[plush kernel]

i k the displacement

[plush kernel]

oh

[plush kernel]

-10m/s =v, time= 4sec ?

[austere notch]

You know the slope and the area can you find t?

v is 0 at 4sec

[plush kernel]

is it 8sec

[plush kernel]

what do i do w that info

[austere notch]

t-4/v = 1/5 and (t-4)*v/2 = 20

Solve and get t and v

I gtg

[plush kernel]

okay thankyou

for ur time

[plush kernel]

s=ut+1/2 at^2
-20= 0+1/2* -5 * t^2
t=2√2
am i right in putting acceleration as -5m/s^2 and displacement as -20m?

so t= (4 + 2√2 )sec

am i right?

[plush kernel]

i didnt get ur part where u put 1/5

[plush kernel]

can u elaborate on why u chose to do that step?

[austere notch]

Because the magnitude of slope is 5

[austere notch]

Yes

[craggy oracle]

@plush kernel

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[plush kernel]

nah , the whole step