# Homework Help: An question

1. Jan 5, 2005

### mfk_1868

an urgent question

http://www.fen.bilkent.edu.tr/~ozbay/Phys101-2004/pastfinal.pdf [Broken] 5th question if anyone can solve please post here very urgent

Last edited by a moderator: May 1, 2017
2. Jan 5, 2005

### dextercioby

The first question is not difficult,however a correct answer to it would solve point b).Without it,u couldn't be able to solve point b).

What are your ideas to approach the problem?You don't expect us to solve it for you,though it's 'urgent'.

Daniel.

PS.Do you know Steiner's theorem??It can be useful for point b).

3. Jan 5, 2005

### mfk_1868

anyone can solve 5th question

4. Jan 5, 2005

### dextercioby

Obviously i can solve the problem for you,however i won't do it.I'll just guide through it.The question at the point "b".Taking into account that is an elastic collision,what phyisical quantities are conserved...?

Daniel.

PS.I hope u see my point.I won't be in your shoes tomorrow at the exam.

5. Jan 5, 2005

### mfk_1868

can you tell me the answer i found it right now 12M/13 can you check this?

6. Jan 5, 2005

### dextercioby

How did u get that answer??I'm not saying it's good,i'm not saying it's bad,just wanna know how u got it.The method is far more important than the result itself.

Daniel.

7. Jan 5, 2005

### mfk_1868

i cant post it but i made 3 equalities angular momentum cons lineer momentum cons and K.E cons now can you tell the answer please it is very importqnt

8. Jan 5, 2005

### mfk_1868

con=conservation

9. Jan 5, 2005

### dextercioby

Why didn't u say that in the first place??You made me think that u were totally 'lost'... :tongue2:
From the angular momentum conservation,u got the angular velocity of the ruler,okay??
From the conservation of linear momentum u got the linear velocity of the ruler,okay??
With these 2 values,u got back into the KE conservation law and using the Inertia moment with a correct value,u got "m".In that case i get
$$m=\frac{M}{1+\frac{12d^{2}}{L^{2}}}$$

Daniel.

PS.One of us is wrong...Don't know who. I may have messed up my calculations,though.

10. Jan 5, 2005

### dextercioby

I found rather dubious that your answer does not depend upon the distance parameter 'd'.If 'd=0 (the puck hits the stick in its center of mass),then the stick should not rotate and the masses should be equal.
My answer satisfies this logics.Yours not.

Daniel.