15.One girl was involved in a bus crash. She told the police that she was seated in the last line of seats and that when the bus stopped or crashed, one big bag that was in the front of the bus flew backward and hit her, breaking her arm Is this likely to have happened? Explain your answer

It is not likely.

Explanation:

When the bus is moving forward, all the objects inside of it also are moving forward.

Now, as the objects inside the buss are not fixed to the bus, if the bus suddenly stops the objects inside of it will keep moving forward, because of the conservation of the momentum, defined as the quantity of motion (Similar to when you are in a car and it suddenly stops, you can feel the forward impulse).

Then is not likely that, in a case where the bus stops suddenly, an object inside the bus flies backward in opposite direction to the previous movement of the bus.

the part of the wave he is travelling on is the crest