What is produced by the rapid changes of the electric field?

What force caused some of these little dots to form big dots

Abody mass of 8.0 kg is acted upon by two forces, 30 n and 40 n. find the acceleration of the body if the forces are (a) along the same direction and (b) exactly in opposite directions answers that are incorrect and irrelevant will be reported and points will be taken back

Acar from the garage is moving to the north along a straight highway and stops after 1 hour for refueling at a gasoline station 80 km away from where it started. how will you describe the motion of the car.? compute for the average speed of the car.