Solving Angular Momentum Problem: Why Answer Differs from Book

[UrbanXrisis]

The problem is http://home.earthlink.net/~urban-xrisis/clip002.jpg .

I got a different answer from what my book tells me and I want to know why. Angular momentum is:
$$L=I \omega$$
So... the moment of inertia for the block would be:
$$I=((M+m)l^2)$$
since the rod has negligible mass, it will not have a moment of inertia.
$$\omega=v/r=v/l$$
$$L=\frac{(M+m)l^2v}{l}$$
$$L=vlM+vlm$$

my text gives an answer of $$L=mvl$$
I don't understand what I misunderstood

 

[SpaceTiger]

my text gives an answer of $$L=mvl$$
I don't understand what I misunderstood

Try again without assuming that the block/bullet combination are moving at the same speed as the original bullet. You'll need to consider conservation of linear momentum.

 

[thepatientmental]

.

There could be a few reasons why your answer differs from what is given in the book. First, it is possible that there is a mistake in either your calculation or in the book. Double check your calculations and make sure you are using the correct formulas and units. Also, make sure you are using the correct values for the variables (mass, length, velocity) in the problem.

Another possibility is that the book is using a different approach or simplification in their solution. They may be assuming certain conditions or ignoring certain factors that you have taken into account. It would be helpful to compare your solution step by step with the one given in the book to see where the differences arise.

Lastly, it is important to note that there can be multiple ways to solve a physics problem and still arrive at the correct answer. It is possible that both your solution and the one given in the book are correct, but just differ in their approach or assumptions. In this case, it would be worthwhile to understand the reasoning behind both solutions and see if they can be reconciled. Consulting with your professor or a tutor can also help you better understand the problem and arrive at the correct solution.