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tbarker5
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Homework Statement
Physicians perform needle biopsies to sample tissue from internal organs. A spring-loaded gun shoots a hollow needle into the tissue; extracting the needle brings out the tissue core. A particular device uses 8.4 needles that take 81 to stop in the tissue, which exerts a stopping force of 38 .
How far into the tissue does the needle penetrate?
Homework Equations
Just F=ma and J=Ft, the same thing really.
The Attempt at a Solution
So I calculated J by multiplying the force through the time. I got 3.1x10^-3 m/s
Then I did the following:
Δp=J
m(v2-v1)=J
v1=-J/m ; assuming v2 equals zero since the needle stops
v1=-2.604x10^-5 m/s
Then I used a kinematic to solve for the acceleration:
v2=v1+aΔt
0=v1+aΔt ; once again assuming v2 equals zero since the needle stops
a=v1/Δt
a=3.2148x10^-4 m/s^s
Using another kinematic now that i know the acceleration:
Δd=v1Δt+(1/2)a(Δt)^2
Δd=1.054x10^-6 m.
Anyways I rounded it to 1.1*10^-6 m since it wanted the answer to two significant figures. This was wrong and I really don't know where I went wrong. Any help would be greatly appreciated