IIT JEE , AIEEE Forum - Physics , Mechanics

vikhi72

A BALLOON is ascending vertically

with an acceleration of 0.4m/s^2 . Two

stones are dropped from it at an interval of

2 sec . find the distance between them

after 1.5 sec after the second stone is

released. take g=10m/s^2.

pls do it

vikhi72

help me!!!!!!!!!!!!!!!!!

vikhi72

i will rate surely

vikhi72

experts tlz help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

sankydreams

distance travelled by balloon in two secs when initial velo is u
= 2u + 0.8
final velo = u + 0.8

both stones will have an initial upwards velo u
for first stone
u = u
t =3.5
a = -g
s = 3.5u - 61.25

for second stone
u = u + 0.8
t= 2
a=-g
s=2u + .16 - 20

the sec stone inially 2u + 0.8 m away
so s for second stone = 4u + .96 - 20

difference = .5u + 42.21
if u = 0
ans = 42.25m

correct if i m wrong
rate if this helps u...

rshm15varma

hey is the answer 50 m

vikhi72

answer is actually 52 written in the book .can u say me the method

gomurali

Sanky will you pl tell me why you have taken u as 0

gomurali

Sanky will u explain y u have taken u as zero

catch_arnnie

the ans. is 52m

consider the motion in the frame of reference of the balloon.
=> the acceleration of the stones become 10.4 m/s^2

when the stones are dropped their initial velocities are zero

we have to find the distance between the stones after 1.5 sec(i.e after the 1st stone is dropped) & after 3.5 (i.e. 2 + 1.5 seconds after the 2nd stone is dropped)

S(1) = (1/2) * 10.4 * (1.5)^2
S(2) = (1/2) * 10.4 * (3.5)^2

distance (d) between the stones = S(2) - S(1)
d = 5.2 * [ 12.25 - 2.25 ]
d = 52 m (ans.)

gomurali

why? the initial velocity of the two stones becomes zero. they are not dropped from the balloon which is stationary nor their initial relative velocity is zero as they are dropped at different incidents . I feel this idea is wrong.

gomurali

why? the initial velocity of the two stones becomes zero. they are not dropped from the balloon which is stationary nor their initial relative velocity is zero as they are dropped at different incidents . I feel this idea is wrong.

catch_arnnie

see, the stones are just dropped from the balloon, so, relative to the balloon(i.e. in frame of reference of the balloon or considering the motion when the balloon becomes stationary) their initial velocity becomes zero. [try to visualise it]....

prathyu

Mr. Arnnie can u please explain it a bit more clearly please

a0shubham79

is the answer 48m

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