- #1
danielamartins
- 9
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Homework Statement
There's a stationary block (m1=1,5kg) in a table (Coefficient of Friction=0,4). A bullet passes through the block and hits a person. The block moved 1,2m. Calculate the velocity of the bullet (mb=0,0079kg and vib=709,88m/s) when it hit the person.
Homework Equations
W(f) = ΔKE
Pix=Px
The Attempt at a Solution
W(f) = ΔKE
v1 - velocity of the block after being hit by the bullet
μ - coefficient of friction = 0,4
d - distance - 1,2 m
- m1×g×μ×d=0- 1/2×m1×v1^2
v1= 3.098 m/s
Then, mb= 0,0079kg and vib=709,88 m/s:
By conservation of momentum:
Pix=Px
p(ix,b)+p(ix,1)= p(x,b)+ p(x,1)
mb×vib+m1×vi1=mb×vb+m1×v1
vb= 121,65 m/s
So, basically, this is what I did. I had to make up the values for the mass of the block and for the distance it traveled.
The thing is, is this analysis right? Because slowing down that much after passing through a block of wood doesn't seem right. Any thoughts?