Mechanics

ANIRUDH PEDAPROLU's Avatar
Cool goIITian

Joined: 20 Dec 2006
Post: 31
7 Feb 2007 22:08:31 IST
0 People liked this
27
1984 View Post
who's creative?
Engineering Entrance , Medical Entrance , AIPMT , JEE Main , AIIMS , JEE Advanced , Physics , Mechanics

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.]



Comments (27)

  • 1
  • 2
  • GO
  • Go to Page...
sagarbhale's Avatar

Cool goIITian

Joined: 4 Feb 2007
Posts: 40
7 Feb 2007 22:12:13 IST
1 people liked this

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??
ANIRUDH PEDAPROLU's Avatar

Cool goIITian

Joined: 20 Dec 2006
Posts: 31
7 Feb 2007 22:16:23 IST
0 people liked this

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
Anshuman Johri's Avatar

Blazing goIITian

Joined: 27 Jan 2007
Posts: 559
7 Feb 2007 22:19:45 IST
0 people liked this

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's Avatar

Cool goIITian

Joined: 4 Feb 2007
Posts: 40
7 Feb 2007 23:10:33 IST
0 people liked this

aniruddh...thats what i said dident i???
SAME FOR BOTH!!!!!
Gautam sharma's Avatar

Cool goIITian

Joined: 25 Jan 2007
Posts: 30
8 Feb 2007 00:12:39 IST
0 people liked this

it wd b the same
neil sabnis's Avatar

Cool goIITian

Joined: 6 Feb 2007
Posts: 57
11 Feb 2007 23:58:02 IST
0 people liked this

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 Prakash's Avatar

Blazing goIITian

Joined: 7 Dec 2006
Posts: 504
12 Feb 2007 13:31:21 IST
0 people liked this

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
Shashank Ganesh's Avatar

Cool goIITian

Joined: 12 Feb 2007
Posts: 51
12 Feb 2007 21:42:52 IST
0 people liked this

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
neil sabnis's Avatar

Cool goIITian

Joined: 6 Feb 2007
Posts: 57
12 Feb 2007 22:38:34 IST
0 people liked this

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

Cool goIITian

Joined: 4 Feb 2007
Posts: 40
13 Feb 2007 20:36:49 IST
0 people liked this

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's Avatar

Cool goIITian

Joined: 10 Feb 2007
Posts: 53
13 Feb 2007 20:58:38 IST
0 people liked this

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........

Blazing goIITian

Joined: 7 Feb 2007
Posts: 544
13 Feb 2007 21:07:18 IST
0 people liked this

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's Avatar

Cool goIITian

Joined: 4 Feb 2007
Posts: 40
13 Feb 2007 21:13:14 IST
0 people liked this

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!!
Anshuman Johri's Avatar

Blazing goIITian

Joined: 27 Jan 2007
Posts: 559
13 Feb 2007 21:13:59 IST
1 people liked this

kghedriu,
 
The force applied by the gun is impulsive and so it provides a certain momentum to the bullet. Once the bullet is fired there is no force exerted by the gun on the bullet. So the acceleration acting is only the acceleration dut to gravity. So the answer has to be c
sagarbhale's Avatar

Cool goIITian

Joined: 4 Feb 2007
Posts: 40
13 Feb 2007 21:17:39 IST
0 people liked this

oh i c what you mean anshuman...perhaps you can elaborate mathematically so i'll understand better..please!!!
rohan sen sharma's Avatar

Cool goIITian

Joined: 3 Feb 2007
Posts: 50
13 Feb 2007 23:39:59 IST
0 people liked this

well it is a damn simple ques.the only prob is that we r gettin confused betwn vel and  acc.what johri said is absolutely correct.the gun gives an impulse to the bulletwhich is responsible for the initial vel.
but after that both the bullet travel under gravity.
so both are under same acc ie g.
001sri's Avatar

Scorching goIITian

Joined: 28 Dec 2006
Posts: 205
14 Feb 2007 12:25:45 IST
0 people liked this

same for both indeed.
the force u r taking of abt gun is an impulse so it impart only initial velosity n no acc.
close this chapter here.
vash's Avatar

Cool goIITian

Joined: 10 Feb 2007
Posts: 53
14 Feb 2007 12:58:17 IST
0 people liked this

but it has some initial acceleration by the gun, the impulse and the acceleration can't be neglected. so there is an acceleration which continues thruout and adds upto g. so height matters. i think i only started the concept of the gun and perhaps i am only givin it a end. or mayn't be!!!!!!!!
Anshuman Johri's Avatar

Blazing goIITian

Joined: 27 Jan 2007
Posts: 559
14 Feb 2007 14:37:15 IST
0 people liked this

Hey vash,
 
Where in the world did u get the idea of initial acceleration of the bullet by the gun?
 
Impulse=Effect of force acting for a short interval of time=Change in momentum
 
=>I=mv
 
And dude, height dosent matter as only the acceleration is asked which has nothing to do with the height.



Quick Reply


Reply

Some HTML allowed.
Keep your comments above the belt or risk having them deleted.
Signup for a avatar to have your pictures show up by your comment
If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team
Free Sign Up!

Preparing for JEE?

Kickstart your preparation with new improved study material - Books & Online Test Series for JEE 2014/ 2015


@ INR 5,443/-

For Quick Info

Name

Mobile

E-mail

City

Class

Find Posts by Topics

Physics

Topics

Mathematics

Chemistry

Biology

Parents Corner

Board

Fun Zone

Sponsored Ads
Vertical Limit

Top Contributors
All Time This Month Last Week
1. Bipin Dubey
Altitude - 16545 m
Post - 7958
2. Himanshu
Altitude - 10925 m
Post - 3836
3. Hari Shankar
Altitude - 9960 m
Post - 2185
4. edison
Altitude - 10815 m
Post - 7797
5. Sagar Saxena
Altitude - 8625 m
Post - 8064
6. Yagyadutt Mishr..
Altitude - 6330 m
Post - 1979