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Homework Statement
A bullet of mass m strikes an amor plate with initial velocity v0. As the bullet burrows into the plate, its motion is impeded by a frictional force which is directly proportional to the bullet's velocity. There are no other forces acting on the bullet.
-Use Newton's Second Law to set up an IVP for the position of the bullet
-How thick should the plate be to stop the bullet?
Homework Equations
[None given with problem]
The Attempt at a Solution
I attempted to use a modified version of a harmonic oscillator formula, where there is no spring. Only the momentum of the object and the friction force resisting it.
m*d^2x/dt^2-kdx/dt=0.
However, in solving it I've run into a problem. While I got an equation for x, x(t)=v0*e^Rt/(R-1)-v0/(R-1) (where R=m/k), trying to use that to find the time at which the bullet stops yields
0=v0*R*e^Rt/(R-1)
e^x=/=0, regardless of x, so there is no possible time at which dx/dt=0.
Is my model flawed, or have I made some other error?
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