/sci/ - Science & Math

[Anonymous No.7490345]

AP Physics starter here. Need your help /Sci /

>The speed of sound in the air is 343 m/s. Using the relationship 3.3 feet in a meter, 5280 feet in a mile, and the time relationships you know, determine the speed in miles per hour.


The answer is already diven, but I don't know what would the formula be.

Can someone please explain?


Yes, I know, easy question, should have previous knowledge of it, bla, bla. "If you don't know how to convert just kill yourself."

I know all of that, thing is I know it's s challenging class and I'm not about to back out because it's a "difficult" class.

I'm not the smartest kid around but I'll bust my ass and I'll get this right.

[Anonymous No.7490355]

Multiply by 3.3 to get ft/s then divide by 5280 to get miles/s then multiply by 60^2 to get to miles/hour.

[Anonymous No.7490357]

>>7490345
343m/s multiply by 3.3ft/m gives you 1131.9ft/s
1131.9ft/s divided by 5280ft/mi gives you .214375mi/s
.214375mi/s multiply by 3600s/hour gives you 771.75mi/hour

[Anonymous No.7490361]

>>7490345
there is no "formula" it is just simple dimensional analysis.
(343 meters/1 second)*(3.3 feet/1 meter)*(1 mile/5280 feet)*(60 seconds/1 minute)*(60 minutes/1 hour)
You need to treat the 3.3 ft/m, 5280 ft/mi, and time conversions as being equal to 1. They are identities, so you can flip them around however you need to to be able to cancel things out and come up with an answer in mph.

Also
>kill yourself

[Anonymous No.7490371]

First, your mindset.

You will drown in AP Physics if you ask yourself "what's the formula". This is not babby physics. The questions do not consist of "use the 3rd item on the formula sheet and this givens to find the 1 unknown". You need to start LEARNING the material. That means understanding what's going on. The only way to understand these things is to try to figure them out using your brain. If you do that, you will find the class infinitely easier than your friends who memorize formulas.

Now, your answer.

If your speed is 343 m/s, then in one second, sound will move 343 meters. But you know that there are 3.3 feet in a meter, so in 1 second, you move 3.3 * 343 = 1131.9 feet in a second. That is, 1131.9 ft/s. Next, there are 5280 feet in a mile, so you're moving 0.214 miles/second. Finally, there are 3600 seconds in an hour (60 minutes * 60 seconds), so if sound moves .214 miles/second, it moves 3600 * .214 = 771.75 miles/hour.

DON'T memorize magic formulas. DO think through problems until you understand them. Only then will you actually learn the content, and do well.

[Anonymous No.7490395]

I can understand how this can be a difficult concept for some so don't feel bad anon. The process for figuring out a problem like this is actually very simple, just break it down:

first identify your variables, in this case they are all units of speed.

Call the starting speed "x" (or whatever really)
Call the ending speed "y"

Now we are trying to figure out what turns x into y, we do this by multiplying by constants so next
Identify your constants:
3.3 feet per meter
5280 feet per mile
60 seconds per minute
60 minutes per hour

Since we aren't doing anything except division and multiplication we don't have to worry about order of operations, all we have to figure out is what is being divided and what is being multiplied.

Speed is measured distance/time

Think of this as a fraction, because that's basically what it is. It is 1/1. 1 meter/ 1 second. So just put the distance measurements on top and the time measurements on bottom.
This is gonna come out ugly cuz I'm posting from my phone, but basically it should end up looking like this:

Y=x* ((3.3*5280)/(60*60))

Since x is given (343) simply put it into the equation and find the value of y

Also not sure what your teacher is looking for here but in most math classes you are expected to reduce fractions and so your actual function would end up being x times a constant

[Anonymous No.7490401]

You really should drop if you cannot do dimensional analysis.

[Anonymous No.7490403]

>>7490395
And I just realized I got it backward, multiply by the time constants and divide by the distance constants. This is the tricky part of these types of problems, which is why it also very useful to use some scratch paper to keep track of what you are doing

[Anonymous No.7490808]

>>7490345
You have no place in an AP science course if you can't do dimensional analysis.

My recommendation would be to just take the regular course or maybe even chemistry because both subjects are pretty huge on dimensional analysis.

[Anonymous No.7490840]

>>7490808
I'm sorry, but isn't AP science where you learn dimensional analysis? I've been out of school a long time but the first time I heard about dimensional analysis was fluid mechanics in my sophomore year of college, though it wasn't the first time I performed it--I just did it without knowing it was called dimensional analysis.

[Anonymous No.7491155]

[Anonymous No.7491389]

This is just converting units. Convert the m/s to ft/s. Then convert to mi/s. Then convert to mi/hr.

[Anonymous No.7491408]

>>7490371
>AP physics is not babby physics
kek

>>7490345
This is an 18+ imageboard. Pls go.