Answer:
(a) θ= 43.89°
(b) 

Explanation:
Ball 1:

Ball 2:

As the collision is elastic, it means that kinetic energy and momentum are conserved. Following that, we apply the law of conservation of energy and momentum:

and

Where u is the velocity before the collision, and v are the velocities after the collision. Both previous equations can be simplified as:

and

This because the two balls have the same mass. We know that the cue ball is deflected and makes an angle of 30°. From conservation in x-direction, we get::

and

Solving we get:

From conservation in y-direction, we get:

From this, we solve this equation system and get the answers. Remember to add 30° to the angle obtained.
Answer:
q2 = -1.61*10^-5 C.
Explanation:
It was given that,
F = 0.985N
q1 = +8.40 X10-6 C
q2 = ?
r = 1.11 m
k = 9 x 10^9 (standard)
It generally follows that, if force is attractive, charge will be negative.
force, F = kq1q2/r^2
0.985 = 9*10^9*8.40*10^-6*q2/1.11^2
75600q2 = 0.985*1.11^2
75600q2 = 1.2136
q2 = 1.2136/75600 = 1.60529
q2 = -1.61*10^-5 C.
When mass is doubled, KE is doubled.
When speed is doubled, KE becomes 4 times as great.
When both are doubled (last choice), KE is multiplied by 8 .
I can't decide between A and B, but B seems more likely to me. Even though the molecules don't look like they're moving, the area of contact is slightly more compressed.