Position of a moving body?
15. a car travels a certain distance with a speed of 50 km. p.h. and retums with a
speed of 40 km. p.h. calculate the average speed for the whole journey. (hint
suppose that the certain distance travelled by the car with a speed of 50 km/h
is x so that he total distance travelled becomes x + x = 2x)

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