Block and the bullet

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Homework Statement


Which equation could adequately be used to determine how high the block goes after being hit by the bullet (a height h)? (see figure)


(m+M)gh+ksh=1/2(m+M)V^2
(m+M)gh+1/2ksh^2=1/2(m+M)V^2
(m+M)v+ksh=(m+M)V

Homework Equations


KE=1/2mv^2
Ugrav=Mgh
PE of spring = 1/2ks(s^2 final - s^2 initial)

The Attempt at a Solution



Based off of the equations, I believe the answer should be the second equation. I don't understand what else it could be..

I have only one attempt
 

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  • #2
SammyS
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Homework Statement


Which equation could adequately be used to determine how high the block goes after being hit by the bullet (a height h)? (see figure)


(m+M)gh+ksh=1/2(m+M)V^2
(m+M)gh+1/2ksh^2=1/2(m+M)V^2
(m+M)v+ksh=(m+M)V

Homework Equations


KE=1/2mv^2
Ugrav=Mgh
PE of spring = 1/2ks(s^2 final - s^2 initial)

The Attempt at a Solution



Based off of the equations, I believe the answer should be the second equation. I don't understand what else it could be..

I have only one attempt
Some of the variables in those equations need to be definrd for us.

I see L1, m, v, and h in the figure.

What are k, s, M, V, an s without k ? Is that ks rather than k⋅s ?
 
  • #3
907
88
Maybe you could explain why you think it couldn't be the other two equations you excluded?
 
  • #4
87
0
Maybe you could explain why you think it couldn't be the other two equations you excluded?
Because the other two equations are missing components to their equations
 
  • #5
87
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Some of the variables in those equations need to be definrd for us.

I see L1, m, v, and h in the figure.

What are k, s, M, V, an s without k ? Is that ks rather than k⋅s ?
1/2ks(s^2 final - s^2 initial)

ks = spring constant (k_s_)
(s^2 final - s^2 initial) = final stretch - initial stretch
v= velocity
m=mass1
M=mass2
 
  • #6
907
88
Because the other two equations are missing components to their equations
And what components do these two equations have that are missing that the other one isn't?
 
  • #7
87
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And what components do these two equations have that are missing that the other one isn't?
(m+M)gh+ksh=1/2(m+M)V^2 the spring constant should be 1/2ksh^2 not ksh
(m+M)gh+1/2ksh^2=1/2(m+M)V^2
(m+M)v+ksh=(m+M)V Ugrav should be (m+M)gh instead of velocity multiplying the masses (m+M)v, also (m+M)V is missing V^2
 
  • #8
907
88
I think you have your answer then.
 

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