Theres some calculations in this problem that I just dont get...(adsbygoogle = window.adsbygoogle || []).push({});

Start with the equations for initial and final momenta and kinetic energies and derive the

theoretical equation for the ratio fo [tex]K_f[/tex] to [tex]K_i[/tex]

[tex]P_i=Mv_i[/tex]

[tex]P_f=(M+m)v_f[/tex]

[tex]K_i=1/2Mv_i^2[/tex]

[tex]K_f=1/2(M+m)V_f^2[/tex]

[tex]K_f/K_i=1/2(M+m)v_f^2/1/2Mv_i^2=M/(M+m)[/tex] this part I dont get. I only get

[tex](M+m)/M[/tex] and im assuming that [tex]v_f[/tex] and [tex]v_i[/tex]

cancel out...

I basically solved for [tex]M=P_i/v_i[/tex] and [tex](M+m)=P_f/v_f

[/tex]

I plug it in to kinetic energy equations and get [tex]K_f/K_i=P_f/P_i[/tex] I guess [tex]

v_f[/tex] and [tex]v_i[/tex] cancel out? Is this answer correct?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Kinetic energy and momentum

**Physics Forums | Science Articles, Homework Help, Discussion**