How Do Kinetic Energies Compare When Two Bodies Have Equal Momentum?

[alijan kk]

Homework Statement

4. Two bodies of mass m1 and m2 have equal momentum their kinetic energies E1 and E2 are in the ratio.

ans. m2 : m1[/B]

Homework Equations

E1=E2
P= mv

The Attempt at a Solution

E1=E2
1/2M1v^2=1/2M2v^2
(Mv^2)/2=(M2v^2)/2
multiply both side by 2
mv^2=2(m2v^2)/2
mv^2= m2v^2

what should i do now? or the attemp is full wrong.

 

[Mastermind01]

Your attempt is wrong. How did you get E1 = E2?

By the given question we have equal momentum $m_1v_1 = m_2v_2$ We have to find out the ratio $\frac{\frac{1}{2}m_1v^2_1}{\frac{1}{2}m_2v^2_2}$ . Try to get the second ratio using the first equation.

 

[alijan kk]

Your attempt is wrong. How did you get E1 = E2?

By the given question we have equal momentum $m_1v_1 = m_2v_2$ We have to find out the ratio $\frac{\frac{1}{2}m_1v^2_1}{\frac{1}{2}m_2v^2_2}$ . Try to get the second ratio using the first equation.

i don't know how to get the second ratio

 

[Mastermind01]

i don't know how to get the second ratio

Well notice how you have to get $v^2_1$ and $v^2_2$ . So first off you square both sides and then try to remove the extra $m_1$ and $m_2$

 

[alijan kk]

Well notice how you have to get $v^2_1$ and $v^2_2$ . So first off you square both sides and then try to remove the extra $m_1$ and $m_2$

i got

m1v^2=m2v^2 right?

should i square both side now

 

[Mastermind01]

i got

m1v^2=m2v^2 right?

By squaring the equation you should get $m^2_1v^2_1 = m^2_2v^2_2$

 

[alijan kk]

By squaring the equation you should get $m^2_1v^2_1 = m^2_2v^2_2$

how can i get :-'

 

[alijan kk]

give me the equation that i should try to solve

 

[Mastermind01]

Well using the equation $m^2_1v^2_1 = m^2_2v^2_2$ you should get $\frac{m_1v^2_1}{m_2v^2_2} = \frac{m_2}{m_1}$

 

[haruspex]

give me the equation that i should try to solve

In your original attempt your very first equation was wrong. You wrote E1=E2. As Mastermind explained, that is not what you are given. You are given p1=p2, where p_i=m_iv_i. I see no evidence that you have understood that.
Start again with the given information and show all your steps. Do not write "I got ...".