A speed that will permit a train or other equipment to stop within one half the range of vision short of a train, engine, railroad car, man or equipment fouling a track, stop signal or a derail or switch lined improperly. When a train or engine is required to move at restricted speed, the crew must keep a lookout for a broken rail and not exceed 20 mph:

Astone is dropped with no initial velocity from the top of a cliff and hits the ground a time of 3.9 s later. what is the height of the cliff, in units of meters? you may assume that air resistance is negligible. give the answer as a positive number question 15 a figure skater is rotating at a rate of 200 revolutions per minute. what is the angular speed, in units of rad/s? 200 o 20.9 12000 o 3.33

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion