You're in a market debating which variety of apples to buy. Picking up and inspecting a red apple in each hand, your mind suddenly drifts to the fond times you had in the great ville de Paris. It's as if you're smelling still the delicate nuances of Parisian croissant, again tasting the hidden textures of Aurélien's café au lait. Suddenly, you hear someone shouting your name. "Peachacid!" You turn around and are completely bewildered to see Aurélien in your nowhere neck of the woods. In a thick parisian accent he says, "Ça alors ! Comment ça va?"
I have lived in both North America and the South Pacific; my answer is: Yes, it would be a normal response to show concern for your friend (as in, asking, if he is hurt). Also, depending on the circumstances of the fall the wow may refer to a spectacular fail at some stunt which may have injured your friend, in which case the wow could be an exclamation of admiration/appreciation/awe (you might have to be a fan of stunt riding to understand this one). Or, if the fall was caused by an unexpected collision (for example, someone is riding past the driveway and your friend is leaving the driveway and they collide) the wow could be used as an exclamation of surprise at the unexpected occurrence; said by you, your friend or the other person. Here, wow would represent only an exclamation of surprise. In my adapted scenario, either your friend or the other person would likely be upset or shocked by the accident and rather than saying, "Wow! are you okay? one of them might use an exclamation or an expletive of complaint or annoyance. Jeez, which is another option would work better here (An example of the given scenario minus the concern for whether or not the person being addressed was hurt would be, "jeez, you need to watch where you are going loser!" in which case the speaker is expressing anger/annoyance towards the other person).
Jeez may not be as widely used or understood as wow. Wow would rate as a polite exclamation where jeez (a type of slang derived from expletive use of "Jesus" - another form being "jeez-us") would most frequently be an expletive type of exclamation. Where wow and jeez (or jeez-us) can differ the most is that wow can only really have a negative use, if and when, spoken with sarcasm ("wow, aren't you smart," meaning I am not impressed by whatever you just said or did) some people consider jeez to be simply an exclamation rather than an expletive which is why it can be more versatile in its use than wow. An example where jeez would normally be more appropriate than wow to express the intended meaning would be where you do not want to do something, "jeez, I do not want to die like that," (having seen a car plummet from a cliff, burst into a ball of fire and smash into jagged rocks at the bottom). Here the use of wow tends more towards a meaning of awe (wow, what a way to go/die)
As in all things, interpretation and appropriateness of use is more to do with the age of the person and the regional locations they are used in, than the words themselves. In the case of your example what you would be expressing to your friend is acknowledgement of the accident and that you are concerned for his/her wellbeing. Using different words so that you might have comparison for interpretation of meaning, you could have said, "hey/yo dude (used here for, "my male friend" especially in North America), I saw what happened, are you okay/hurt?
Wow! What a long explanation. Geez I hope this helps or I just wasted a bunch of my time :)
It is used to mean "how are you."
Comment ça va ? = How is it going?
Comment vas-tu/allez-vous ? = How are you going?
The latter could be taken to mean what the English sentence does, namely, "how are you getting to where you are going." "Comment ça va ?" (casually "Ça va?" or "Ça va bien ?") is more common, because there is no ambiguity.
Again, another test where we havent been taught any of the words and given no explanation or reasoning behind the sentence structure. I'm forced to look at the answer and basically memorize rather than learn why the sentence is the way it is. Im passing but dont feel like im learning anything in this Phrases course.
"Jeez" is a short form of "Jesus" and is considered less disrespectful than using Jesus' name when expressing frustration/anger/surprise by many Christians. I would say that "jeez" is most commonly used to express annoyance, so it seems very strange to have it in this sentence.
"Ça alors !" is an exclamation of surprise and depending on the context and whether it is a good surprise or a bad one, it can be translated differently in English. "Wow" would be a good surprise, "jeez" not so good. One translation that could work in either case is "OMG!" Where the tone of voice would show the difference. The same is true with "ça alors" thé tone of voice and intonation indicates whether it is good or bad. Unfortunately a computer voice doesn't help :( In the context where "ça alors" is followed by "comment ça va ?" it very likely is expressing surprise at coming across a friend and then asking how he/she is.