Mary starts from her house, walks 80 meters south, and stops to chat with her aunt on the sidewalk. after chatting for a few minutes, she walks 125 meters to the west to meet a friend and then walks 45 meters north with her friend to a cafe for lunch. overall, she takes 10 minutes to do all this. what is mary’s average speed?

Average speed = (total distance covered) / (time to cover the distance)

Total distance = (80m) + (125m) + (45m) = 250 meters

Overall time = 10 minutes

Average speed = (250 meters) / (10 minutes)

Average speed = 25 meters/minute

Since we're only looking for average speed and not velocity, we don't care about any of the directions, and we don't need to calculate Mary's displacement.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.

distance = 150m

displ = root (50 ^2 + 100^2)

root(2500+10000)

root 125000