Some good revision problems

Yesterday Philip was frustrated at the lack of gud problems...I am posting some for everyones practice..........2009 aspirants should solve them and put up solutions here for 2010 students to learn.............

Some might be easy.......but all are conceptual[1][1].....

Q1 A uniform rod of length 2a and mass m is rotating in horz plane about a smooth fixed pivot through the centre of rod with a constant angular velocity w rad/s.A particle of same mass moving with speed aw/4 opposite t orod strikes one end of the rod perpendicular to it.If e=1/2,calculate angular velocity of rod immediately after collision.

If anyone has problem with my initiative he/she is free to express his/her views...........i wont feel bad at all and i will stop this work at that moment only..[1][1][1][1]

144 Answers

106
Asish Mahapatra ·

is it 9w/32 rad/s in the same direction as before?

btw. its a gud initiative.glad if such things wud come for organic too.
thx dude.

24
eureka123 ·

Q2 A scale is placed in tilted position in vertical plane.The lower end of scale touches the groound.The surface has friction.The scale now falls in such a way that the loweer end is at rest.The other end has velocity of 2m/s when it hits the ground.Find out angular velocity of scale assuming length =1m.Also find velocity of CM of scale.

24
eureka123 ·

let others also try it...........if u r sure then u may post ur solution here using hide feature..........
I will post answer one day after posting the question so that everyone gets ample time to solve it.......[1][1]

3
iitimcomin ·

sorry for poosr handritin............and yaar in q2 is the bottom fixed??????

3
iitimcomin ·

and yaar when to find angular velocity when it is just release or in the end??????

3
iitimcomin ·

@may be for iit(his post is now deleted) ... if its in the end then the angular velocity will simply be 2/1!!!!!! as the other end becomes the iaor as it is at rest!!!!!!and com will hav velocity 1m/s!!!

3
nihit.desai ·

Hey..iitimcomin....its given the initial velocity of the body of same mass is 'opposite' to that of the rod...so inital angular momentum will neative sign before the second term...othrwise i think the concept is correct ...

3
iitimcomin ·

3
iitimcomin ·

jee mai entropy nahin hai!!!!

3
iitimcomin ·

Thermal physics: Thermal expansion of solids, liquids and gases; Calorimetry, latent heat; Heat conduction in one dimension; Elementary concepts of convection and radiation; Newton's law of cooling; Ideal gas laws; Specific heats (Cv and Cp for monatomic and diatomic gases); Isothermal and adiabatic processes, bulk modulus of gases; Equivalence of heat and work; First law of thermodynamics and its applications (only for ideal gases). Blackbody radiation: absorptive and emissive powers; Kirchhoff's law, Wien's displacement law, Stefan's law.

24
eureka123 ·

There was some conflict in last one so this is newer.....
Q3

11
Subash ·

Q2 ans √30?????????

24
eureka123 ·

nops dear....[2].....but keep trying

1
chemistry organic ·

nice handwriting iitimcoming......[1]...1 of my friend had handwriting like u .....

3
iitimcomin ·

yaar for Q 2 at wat moment shud i find w????????????

24
eureka123 ·

when its going to strike dear.........its very easy.....i hope u can wrap it up......[1]

3
iitimcomin ·

at wat point of time shud w be founf?in the beginnig or end?????

24
eureka123 ·

what point of time????????
when it is about to strike........[1]

24
eureka123 ·

and what happened to Q3???????u wanted a thermo question....so i posted it........do solve it,......[1]

3
iitimcomin ·

then its simply 2RAD/S and 1M/S!!!!

3
iitimcomin ·

ohhh uve changed the ques.!!!!!didnt see!!

3
iitimcomin ·

qs. 3 ... W=2(600R)(1/3-1/5)...................

3
iitimcomin ·

ΔU(A TO B)=0

ΔU(B TO C)=nCv(1V2/2R - 3V2/2R)....................

V2 = 2(600R)(1/3).................

ΔU(d TO a)=nCv(5V1/2R - 2V1/2R)

V1=2(600R)(1/5)...................

net ΔU = 0............

ΔU(c to d) = 0 - ΔU(A TO B) - ΔU(b TO c) - ΔU(d TO a).................

Q=W + ΔU(c to d),,,,,,,,,,,,,,,,

THUS EVERTTHIN SOLVED!!!!!!

24
eureka123 ·

yup u r rite iit.........post the solution for Q2 here for others...as 1 day gone.......[1][1]

3
iitimcomin ·

if its in the end then the angular velocity will simply be 2/1!!!!!! as the other end becomes the iaor as it is at rest!!!!!!and com will hav velocity 1m/s!!!

(same as in #8)

24
eureka123 ·

ok....gud job.....

24
eureka123 ·

all 3 have been solved so here is fourth one.....

maybe a sitter.....[3]
Q4 A disc has velocity v and angular velocity w.It strikes a scale of same mass and length 2R at the edge and then sticks to the scale such that scale rotates along extension of radius.Both lie on horz frictionless surface/.Can we apply conservation of angular momentum here?If so write down the eqn.

3
iitimcomin ·

yes we can apply conservation of momentum !!!!!!!!!!!!!!!!!!

24
eureka123 ·

thats true......write the eqn then.....i knew it was very easy.....gave it in hurry

3
iitimcomin ·

since its not pivoted we can conserve ang. mom about any point!!!!!!!!!!!!!

so lets concider the center of the rod!!!!!!!!!!!!!!!!

mvR + I(com)W = [I(com rod)+I(com disc)+mR^2]W/ + mw/R..........

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