IIT JEE , AIEEE Forum - Physics , Mechanics

anirudh1990

A bullet is dropped to the ground from the top of a building while another is fired towards the ground from the same building. Neglect air resistance, the acceleration is:

1)greatest for dropped bullet

2)greates for fired bullet

3)same for each

4)depends on how far they are from the ground.

[only one is correct.]

sagarbhale

same for each i guess as they are both under the gravitational influence...the fired one will only have initial velocity and thus will reach the ground faster

am i correct??

anirudh1990

hi Sagar,
i too had the same opinion but they key paper says that it is the (3)rd option. i.e. same for each

johri_anshuman

The 3rd option is correct as the acceleration due to gravity g is the only accleration acting on both the bullets. So their velocities will be different but they always possess the same acceleration.

sagarbhale

aniruddh...thats what i said dident i???
SAME FOR BOTH!!!!!

gautam_agni_sharma

it wd b the same

sabnisneil

its the same..because acc on the body in motion is always g downwards..so it dosnt matter wheather the body is goin up or down..the acc on each boy must remail g i.e the same......ryt anirudh???

uday_zingtudor

how come it would be the same when u provide extra velocity to the bullet ?

remeber gravitation is the only retarding force

but in this case the fired bullet has acquired some velocity and the other has not

u may visualize it practically

fire a bullet and release the other

sg_90

i think all of u are getting confused between the speeds and the accellerations of the bullet

the speeds are different..... accepted

but here we are being asked abt accelleration.

here accelleration would be the same fr both as gravity the only external force acting onthe bullets

sabnisneil

i think u day dude...u should again go through wht u hv written
acceletation is change in velocity...and not velocity..

sagarbhale

hi neil

uday use the basic defifnition of velocity.....it is CHANGE in velocity upon time and not just velocity

a = dv/dt or in other words a = v-u/t

thus the initial velocity is of no concern with the acceleration
try using the equation with examples mate you'll understand...or simply use deravitives if you know them

vash

i think it depends on the height. as the bullet is fired it attains a tremendous velocity in a short period of time. that means it has some initial acceleration. as it goes down it adds up to the natural g and keep on increasing till it reaches the ground. as in the second case it's just the 'g'. so it matters on the height from where they are fired. i think i am right, but if i am wrong then spot out my mistakes plzzzzzzzzzzzz........

kghedriu

C'mon, then explain this:

why don't we say that there might be another acceleration provided bcos of the force the gun exerts????????

sagarbhale

i did consider that possibility mate...but i don't think the problems means tht..it only means that one bullet has higher initial velocity and the other has the lower...tths how i interpret the problem...i don know about you guys...

if the force of gun is to be considered then the bullet fired from the gun will obiviously have higher acceleration as it has initial acceleration and it is fired in direction of the gravitational acceleration...the two will add up.

cheers!!

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