- #1

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i derived an equation of 1*p^2/2m and im not sure where to go from there.

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- Thread starter philo51
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- #1

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i derived an equation of 1*p^2/2m and im not sure where to go from there.

- #2

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philo51 said:

i derived an equation of 1*p^2/2m and im not sure where to go from there.

First of all, you should ALWAYS be in the habit of making sure all numerical values have the appropriate units. You left this out in your question.

Now you are told that KE1 = KE2, where 1=the bird, 2=ball.

So let p1 and m2 be for the bird, and p2,m2 be the ball. You then have

[tex] \frac{p_1^2}{2m_1} = \frac{p_2^2}{2m_2}[/tex]

Solve for p1/p2. You have everything you need already there.

Zz.

- #3

mezarashi

Homework Helper

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Equate this kinetic energy for the cardinal and the baseball. You will now have the velocity of the cardinal in terms of the velocity of the baseball.

Now momentum is defined as: p = mv

The ratio of momentum is defined as Pcardinal/Pbaseball.

Knowing the relationship between the cardinal's velocity and the baseball will allow you to cancel out the v's and solve ultimately for a constant.

[oh, i was beat lol]

- #4

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hah wow i completely missed doing that thanks!

- #5

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so if p= sqrt(2Km) and P1= P2

sqrt(2K(man)m)=sqrt(2K(woman)m) and if i solve for Km/Kw why doesnt that work out?

- #6

mezarashi

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You are essentially trying to solve for the velocity of the man in terms of the woman's velocity by equating their momenta. Kinetic energy is expressed in terms of mass and velocity. But you know one in terms of the other. In ratio form, they will surely cancel out. It's no different than the original question. Step by step. Good luck.

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