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What is the rotational inertia of the door about the hinges?

  • Thread starter mjdiaz89
  • Start date
11
0
Thank you all for taking the time to help me out. Here's what I'm given:

1. Homework Statement
A solid door of mass M = 19 kg and width = 128 cm is hit at a right angle by a mud ball of mass m = 0.6 kg, which, as Fig. 10–44 shows, hits the door at the edge with speed v = 16 m/s and sticks.


Figure 10-44

(a) What is the rotational inertia of the door about the hinges?
10.377 kg·m2
(b) What is the angular velocity of the door after having been struck?
________ rad/s
(c) What fraction of the initial energy does the moving door–mud ball system retain?
_______


2. Homework Equations
p=mv
I= 1/3mr^2
L=mvr


3. The Attempt at a Solution
-Part A was simply 1/3mr^2
-Part B confuses me because I have to somehow make a linear momentum into a rotational momentum, while not forgetting the moments of inertia. Someone please shed some insight to this simple problem.
-Part C = I need part B :/
 

Answers and Replies

Nabeshin
Science Advisor
2,204
16
Your equation L=mvr is what you need for part B. This will give you the angular momentum of the projectile.
 
11
0
huh?
 

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