MECHANICS


Be serious enough to answer this .. if u know then only answer . . i don't know the answer .. u gotta give me that with explanation ..

29 Answers

1
ANKIT MAHATO ·

nishant bhaiya yelp !!

1
ANKIT MAHATO ·

Q 3 banao read post 26 also !!

33
Abhishek Priyam ·

@prateek
In time dt let water coming out be volume sdx
mass of water coming out =ρsdx
momentum =dP=ρsdxv

F=dP/dt
=ρsdxv/dt
ρsvdx/dt=ρsv2

1
ANKIT MAHATO ·

YELP !! Q 3 !!

1
prateek punj ·

hey yaar i have a doubt how the force exerted by water coming out is ρsv2...please explain.....

1
ANKIT MAHATO ·

in question 3 the rate of production is t2 ... unknown . . .. quantity is minimum at t0 .. not maximum .. solving the differential equation is easy tsk but what is the intial limit .. should i take the initial concentration as zero ..

1
ANKIT MAHATO ·

Nishant Bhaiya . .gr8 solution of 1st question thanks .. !

1
ANKIT MAHATO ·

yup sky i think it is s instead of 5 .. !!

1
skygirl ·

mu is not 5h/V

it is sh/V..

mu has no dimension.

1
skygirl ·

2.)

62
Lokesh Verma ·

dN/dt = t2-λN

when maxima dN/dt=0

so t2=λN(t0)

solve the differential equation above...

dN/dt = t2-λN

now substitute and see :)

62
Lokesh Verma ·

virang!!

See Forces for the spring
1 Force downwards mg
1 force upwards 2mg
Resultant force = mg
Therefore
Total mass of the system = 3m
a = mg/3m
a = g/3 upward for A and downward for B

how do you know that force downward is mg??

you have to first equate it to T

see the whole thing is that T1-T2=ma (spring is massless .. so the tension on both sides of the spring is equal)

Now you have to see that mg-T=ma1
2mg-T=ma2

(you cannot use a1=-a2!!) (because spring is elongable!)

what is the constraint relation??

if the spring is acted by tention T on both sides, then extension is T/k

initially no extension...

iniatilly T is just zero because extension is zero in the spring

hence both accelerate with acceleration of g downwards!

1
ANKIT MAHATO ·

i dont have solution of any of these .. otherwise i would have figured out myself ... dude ..

1
ANKIT MAHATO ·

eureka please see ur solution to 2nd problem again with care !!

1
ANKIT MAHATO ·

YELP !!

1
ANKIT MAHATO ·

Nishant bhaiya .. can u give me a clue

11
virang1 Jhaveri ·

Nishant Bhaiyya
Check post #13 is it rite?

1
ANKIT MAHATO ·

i just remember that force due to water coming out is ... ρsv2
= 2ρsgh ...Max Friction is μmg = (5h/V)(ρV)g = 5ρgh

now i was confused because in the question it is mentioned that friction in the container is not sufficient to keep the container at rest but s is not given so what to do ... also i noticed that μ is not dimensionless ... [11]

11
virang1 Jhaveri ·

See Forces for the spring
1 Force downwards mg
1 force upwards 2mg
Resultant force = mg
Therefore
Total mass of the system = 3m
a = mg/3m
a = g/3 upward for A and downward for B

11
virang1 Jhaveri ·

1.
B)

1
prateek punj ·

#1 dekh....give ur comments...abt it....

1
prateek punj ·

yaar mujhe first ka (d) lag raha hai.....
i think i'm wrong.....pakka

11
Mani Pal Singh ·

WAT IS THE QUESTION[7][7][7]

1
prateek punj ·

yaar iske bare main bhi socho....

62
Lokesh Verma ·

3rd one is of chain reaction

X - > A - > B

in principle i dont think it in syllabus but it is given almost every where... And I strongly advocate knowing this too....

21
tapanmast Vora ·

initial velocity of fluid comin out : √2gh

Momentum towqards rite = ∂M √2gh

So mom. has to bve equal towardsd left.....

aagge [12] [7]

62
Lokesh Verma ·

2nd one is another brilliant question...

the important thing is that initially what will be the velocity of the fluid coming out?

Also apply momentum conservation?

62
Lokesh Verma ·

in the first one also draw the fbd of the spring .. that wil help a lot

it is given that it is massless...

62
Lokesh Verma ·

some one asked this to me just 2 days back

in the first one the most important thing is what is the invariant just after release!

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