# Final Frequency and Kinetic energy change?

## Homework Statement

Hi I know my picture has 2 problems, but lets just focus on the first problem parts a and b.
So for part a it ask for the final frequency after the ant landed, and part b is the kinetic energy difference. Basically the
ant=.01kg, diameter of cylinder is .115m,
the weight of cylinder is .03kg,
and its rotating at 300 rev/min.

## Homework Equations

[/B]
deltaK=Kfinal-Kinital
kfinal=.5*i*w where i is the inertia
i=.5*m*r^2
w=w0+at

## The Attempt at a Solution

For part a I used the the rotational equation formulas, Im not sire if i picked the correct one though. For part b, its based on part a, basically find the kinital and final with the mass changing from .030g t0 .040 cause the ant has its own weight. Part b I understand its jsut part a I am dont really know where to start?

#### Attachments

• Screen Shot 2016-06-14 at 9.53.08 PM.png
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Simon Bridge
Homework Helper
The pic is about a bullet hitting a wooden block.
Note: do not do physics by trying to guess the right formula. Instead, try to figure out what physical principle is at work ... i.e. some sort of conservation law.
Guessing you have a rotating cylinder that an ant drops on ... part b is easier.
Part (a) the frequency will be related to the angular velocity, which is related to both angular momentum and kinetic energy. The kinetic energy is also related to angular momentum.

• CWatters
Omg sorry I uploaded the wrong picture, its this one. Please disreguard the image in my first post. Also for #1 part a, I need to get the final rev/min after the ant falls on it, so I am thinking, w=2*pi*f. But I have two unknowns because I don't know how to get f? unless w= winitial which is 300 rev/min?

#### Attachments

Last edited:
Sorry for double posting but I can't really find Ffinal because I don't see how I can use the initial frequency of 300 to get the final frequency?

CWatters
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