9 and 10 word problem

I’m trying to study for my Physics course and I need some help to understand this question.

Question 37

1. Explain the concept of frames of reference.

Question 38

1. Explain length and time dilation and give an example of when each is observed.

Question 39

1. A train is moving with a speed of 50 miles per hour. A man standing in the rear of a train car throws a ball toward the front of the train with a speed of 10 miles per hour. If a stationary observer outside the train sees this happen, what speed is the ball moving with? Explain your answer.

Question 40

1. Explain any one situation in which light behaves like a particle and one situation in which light behaves like a wave.

Question 43

1. What is nuclear fission? How do you account for the release of a large amount of energy in a nuclear fission process?

Question 44

1. Two events that are simultaneous in one inertial frame of reference will not necessarily be simultaneous in any other inertial frame of reference. Explain.

Question 45

1. Consider a situation where immediately after birth, twins are separated. One continues to live on earth, while the other is whisked away in a space ship at 90% of the speed of light. After 65 years they are reunited. Will they look the same? Show proof of your answer through mathematics.