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.
The force can be calculated by multiplying the mass of the gymnast with her acceleration.
Force = 50 kg × 25 m/s2
Force = 1250 N
A force of at least 1250 N can stop the 50-kg gymnast.
I hope I was able to answer your question. Have a good day.
Answer:A
Explanation: search for a gap in traffic and adjust your speed to the speed of the traffic.
You just told us that Weight = (mass) x (gravity),
and that mass=10kg and gravity = 9.8 m/s².
All we need to do is write those numbers in place of the letters.
Weight = (10 kg) x (9.8 m/s²) = <em>98 newtons</em>.