A400-lb object is released from rest 500-ft above the ground and falls under the influence of gravity. assume the force in pounds due to air resistance is  where  is the velocity of the object in ft/sec, determine the equation of motion of the object. when will the object hit the ground and what is its velocity at the impact

It may seem strange that the selected velocity does not depend on either the mass or the charge of the particle. (for example, would the velocity of a neutral particle be selected by passage through this device? ) the explanation of this is that the mass and the charge control the resolution of the device--particles with the wrong velocity will be accelerated away from the straight line and will not pass through the exit slit. if the acceleration depends strongly on the velocity, then particles with just slightly wrong velocities will feel a substantial transverse acceleration and will not exit the selector. because the acc