- #1
mech-eng
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Homework Statement
The brake mechanism used to reduce recoil in certain types of guns consists essentially of a piston which is attached to the barrel and may move in a fixed cylinder filled with oil as the barrel recoils with an initial velocity v0, the piston moves and oils is forced through orifices in the piston, causing the piston and the barrel to decelerate at a rate proportional to their velocity; that is, ##a=-kv##. Express v in terms of t, x in terms of t, v in terms of x. Draw the corresponding motion curves.
Homework Equations
##\ \displaystyle a=\frac{dv}{dt} \ ##
##\ \displaystyle v=\frac{ds}{dt}##
The Attempt at a Solution
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Substituting -kv for a in the fundamental formula defining acceleration, a=dv/dt, we write
##\ \displaystyle -kv=\frac{dv}{dt} \ ## ; ##\ \displaystyle \frac {dv}{dt}=-kdt##
##\ \displaystyle \ int_v_0^v \, dx = \left. -k \int_0^t \, dt \right \ ##
## \ \displaystyle ln\fracv_{v_0}=-kt ##
I have made mistakes when doing latex. So I paste official solution. I understand most of it but the confusing part is that when integrating why the author did not use integration constant?
Source: Vector Mechanics for Engineers by Beer/Johnston.
Thank you.