What is the only thing that can pull a beam of light towards itself ?

It is really hard for me right know

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.

Which symbol in the first law of thermodynamics represents the sum of the chemical and thermal energy stored in atoms and molecules? a. q b.w c.v d.u