In the absence of air friction, the horizontal component of a projectile’s velocity doesn’t change as the projectile moves.

a. sometimes true
b. always true
c. always false

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?