# The most tragic mistake ever... or something very clever ? (1 Viewer)

#### T-mac01

##### Member
eX-Bhai said:
Hm, I see you have forgotten Galileo's analysis of projectile motion. The vertical component is INDEPENDENT of the horizontal component. So, in essence the horizontal velocity is kept constant (where it undergoes no acceleration), but the vertical acceleration changes (depending on its position on earth). So yeh, good try though, it sounds like something I'd do. But sadly, its wrong. Don't get too worried about it though - its only one mere mark.
Well it's still a shame to lose a mark like that. It's not like he couldn't figure it out. Exams just make people freeze sometimes. And that one mark could make a difference due to the percentage calculation for all our scores.

#### dunno04

##### Member
hyparzero said:
Look at the projectile motion question:

Clearly, the answer is ZERO - its asking for the velocity when it LANDS. If it lands, it's not moving anymore...

Who disagrees?
The horizontal component is always the same
U might be right...u never know

BUT..IF u are wrong
that means the answer is 45m/s
=D

#### gamecw

##### Member
dunno04 said:
The horizontal component is always the same
U might be right...u never know

BUT..IF u are wrong
that means the answer is 45m/s
=D
he knows that...

#### Mumma

##### Member
The answer could not be 0 EVEN if they did mean *after* it lands. They didn't mention frictional forces, but lets assume the ground does produce frictional forces on the ball. This frictional force would have to be infinite for the horizontal velocity to reduce down to 0m/s in 0 time.

#### *yooneek*

##### @UTS...I <3 Jesus
i cant stand that projectile motion goes right over my head... i just cant grasp it...

lol im one of the ones who wrote zero

every single jolly thread i go into that discusses a question from this paper i realise i did the wrong thing!

passing doesnt look like a likely prospect anymore

#### hyparzero

##### BOS Male Prostitute
*yooneek* said:
i cant stand that projectile motion goes right over my head... i just cant grasp it...

lol im one of the ones who wrote zero

every single jolly thread i go into that discusses a question from this paper i realise i did the wrong thing!

passing doesnt look like a likely prospect anymore
join the club, girl! :wave:

#### dom001

##### New Member
Answer is 45ms^-1 to the right. Probably half for omitting the direction.

If you assume 'land' to mean the instant it first touches the ground, it would still technically have this component of its velocity.
It isnt until the ground exerts a force on the ball that the motion is retarded, and eventually stopped - but this doesnt happen instantly (F=dp/dt=m[dv/dt] - as the force is applied, the ball's velocity would gradually approach zero; this is not instantaneous.)

#### glqgkqyeah

##### New Member
Benmc said:
I forgot to.
Well velocity is a vector so it probably does matter.
But hopefully the see that we understood the question enough and just give us the damn mark.

I guess it will not really matter because it already states "horizontal"

wouldn't that mean enough ?

I stated that the horizontal component doesn't change , therefore Vx = 45m/s

This will give enough indication of its direction as it's initial direction is drawn on the diagram.

#### macoboi

##### Member
dom001 said:
Answer is 45ms^-1 to the right. Probably half for omitting the direction.
nah, it'll either be one for no direction, or zero. no half marks in HSC exams

#### muttiah

##### Banned
y do ppl keep saying the answer.. he knows the answer now.. no need to reply 45

#### watatank

##### =)
^^bit rich coming from you...telling everyone off for saying the answer and then putting it down yourself as well...

Well I got what most people got but didn't add direction...oh well.

#### dunno04

##### Member
watatank said:
^^bit rich coming from you...telling everyone off for saying the answer and then putting it down yourself as well...

Well I got what most people got but didn't add direction...oh well.
Direction...U don't need that.

DO u?

#### shinji

##### Is in A State Of Trance
no, i don't thnk so.

horizontal component. of the velocity

im pretty sure as hell i didn't get tht wrong for my trials [besides calculation part. i condemn thee radians!!!!!!]

#### coolzor

##### New Member
Objects moving to the right is positive and objects moving to the left is negative..same as up is positive and down is negative...so i dont think u need direction..but then again..they mite b picky

#### dunno04

##### Member
coolzor said:
Objects moving to the right is positive and objects moving to the left is negative..same as up is positive and down is negative...so i dont think u need direction..but then again..they mite b picky
i dun think u need direction....
DO u?
NooOOOoooo

#### arkanisw

##### New Member
wuddie said:
BOO YEA 45ms all the way... i think i forgot to put 'to the right', does it matter?

technically it shouldnt matter, coz it asks for horizontal component, ie, linearly,

it is + or - to indicate direction, if u wrote 45, as opposed to -45, technically it gives the direction as well

#### MisterPresident

##### Member
45m/s sounds fine to me.

It's implicit in the diagram that it's not to the left.