Q.
A satellite in force free space sweeps stationary interplanetary dust at a rate of dM/dt=αv , where M is mass and v is the speed of satellite and α is a constant. The acceleration of satellite is
Rate of change of mass dtdM=αv.
Retarding force = Rate of change of momentum = Velocity × Rate of change in mass =−v×dtdM =−v×αv=−αv2.
(Minus sign of v due to deceleration)
Therefore Acceleration =M−αv2.