Kinetic Energy help

[grand delta]

Hi

[pastel raft]

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[grand delta]

Letter b is confusing me

So since it's at its apex the velocity is 0 I know that

but im not sure how to find maximum height

So if the initial velocity is 22m/s in this case and the final velocity is 0

[fading wasp]

u can use equations of motion

[grand delta]

Yea I was thinking the same but they require acceleration which I dont have

[gusty solstice]

i can make it very easy for you maybe

[fading wasp]

acceleration is acceleration due to gravity

[gusty solstice]

use energy conservation

[grand delta]

so acceleration in this case is 9.81m/s^2?

[fading wasp]

yes

[grand delta]

Hm, alright

[gusty solstice]

total initial energy = energy at highest point but kinetic energy will be 0

[fading wasp]

but be careful of the sign

[grand delta]

There

[grand delta]

Yea

[fading wasp]

wait nvm u need to use laws of conservation of energy as per the question

dont use kinematics

[grand delta]

Em = Ek + Eg?

So since Ek is 0 that cancels out

I'm left with Em = Eg which Eg = mgh

I'd need to find h?

[gusty solstice]

yes.

u have m you have g

[grand delta]

I dont have Eg

Man I hate these kinds of questions where I need just one thing which idk how to get

[gusty solstice]

total initial energy = total energy at max height

[grand delta]

What is the variable for total initial energy?

[gusty solstice]

since there is no kinetic energy at that height. all the energy is potential energy

[gusty solstice]

mechanical energy. u might use any variable for it as u wish

[grand delta]

Em alright

[gusty solstice]

just mention before attempting

[grand delta]

I cant find the total initial energy at max height

if kinetic is 0 I have only Eg

[gusty solstice]

leme write the solution

[grand delta]

I dont have enough stuff to find Eg

[gusty solstice]

partly.

[grand delta]

Okay

Yea like I said it's just Em = mgh

Nothing else

I dont have 2 of the variables so I cant solve it

[gusty solstice]

total energy at any point will be same. Thats Energy Conservation

until acted upon by a non conservative force obv

[grand delta]

Didn't you say kinetic energy is 0

1/2 * mv^2 is 0

[gusty solstice]

yeah.

yes.

[grand delta]

Oh wait you did A too

Yea I did A

[gusty solstice]

but it still has potential energy

[grand delta]

its easy

OHHHH I put Eg as 107J

I got it

alright

[gusty solstice]

107.2 is total energy. potential energy due to gravity only at maximum height

[grand delta]

I thought 107.2J was only for the height being 30m

Thats one of the things that confuses me about physics stuff, you input stuff from other questions that have different circumstances and it works somehow

[gusty solstice]

u see the sum of kinetic energy and potential energy is total energy which id constant throughout. but the kinetic and potential energy on their own changes with speed and configuration

[grand delta]

Ohhhh so the total energy is constant

I'll keep that in mind

[gusty solstice]

physics is made up of universal laws. its valid throughout

[gusty solstice]

just make sure there is no non conservative force acting. non conservative forces are like friction, air drag, viscous force etc

[grand delta]

Yea

I have a quiz next period so im wrapping things up

[gusty solstice]

just ping to ask anything

[grand delta]

Alright thanks thanks

[gusty solstice]

funfact:- kinematics can be used to do the part 2nd and third.

[grand delta]

Yea the motion equations I was thinking about it

and like the other guy said acceleration is the gravity speed which is 9.81m/s^2?

[gusty solstice]

gravity doesn't have speed but yeah

thats the amount of acceleration earths gravity provides to objects close to it.

[grand delta]

I see

Im a lesson behind so I might do bad on the quiz

[gusty solstice]

nah. trying ur best is the best thing to do

[grand delta]

Im a slow learner but once I get the hang of something I do it really fast

I couldnt keep up with the teacher so I just had to F it

[gusty solstice]

just prepare for ya quiz. good luck

[grand delta]

Thanks bro

[fading wasp]

I know that but since they specifically mentioned for energy conservation I said that

[gusty solstice]

oh i didnt notice that

[grand delta]

Hey mega I need some help on another question

I understand a easily

but b is confusing me

What do I change in the equation v^2 = 2ad?

[gusty solstice]

have u heard of work energy theorem

[grand delta]

Yes

Oh wait no

I thought you were talking about the Em = Eg + Ek

[gusty solstice]

work energy theorem states that work done = change in kinetic energy

[grand delta]

Work done is Wnet?

I searched up the answer for this and it said Ek = 2mad but Im not sure how it became that which is what im trying to figure out

[gusty solstice]

work done is equal to change in kinetic energy

thats work energy theorem

[grand delta]

Wnet = initial kintetic energy - final kinetic energy???

Or is it the other way around?

[fading wasp]

final KE - initial KE

work done by all forces

[grand delta]

I see

Alright I think thats all of them