In the year 1178. five monks at canterbury cathedral in england observed what appeared to be an asteroid colliding with the moon, causing a red glow in and around it. it is hypothesized that this event created the crater giordano bruno, which is right on the edge of the area we can usually see from earth. how long after the asteroid hit the moon, which is 3.84 x 10^5 km away, would the light first arrive on earth in seconds?

1.28 sec

Explanation:

Assuming that the glow following the collision was produced instantaneously, as the light propagates in a straight line from Moon to the Earth at a constant speed, we can get the time traveled by the light applying velocity definition as follows:

V = ∆x / ∆t

Solving for ∆t, we have:

∆t = ∆x/v = ∆x/c = 3.84 108 m / 3.8 108 m/s = 1.28 sec

electric field is a function of 1/r^2

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