# I feel like such an idiot (Help please with unit conversions)

1. Sep 1, 2015

### APAlex

1. The problem statement, all variables and given/known data
How am I supposed to know my unit conversions? like for example 1 pound is equal to 453.592 grams I don't know how people do it, it's like they have it all memorized in their head I can't think of a way for me to be able to memorize any of it or know it am I supposed to do something?

2. Relevant equations

3. The attempt at a solution

2. Sep 1, 2015

### Bystander

Yes. Drill. Mind-numbing repetition of "the alphabet song." There are no pills --- that's still in the realm of sci-fi.

3. Sep 1, 2015

### Staff: Mentor

Welcome to the PF.

As to your question, I know that a kilogram is about 2.2 pounds, but that's about as accurate as that conversion gets for me. I also know that an inch is 2.54cm, but I use that a lot in measuring things. There will just be some things that you do a lot where it's handy to memorize a few conversions (just like you will memorize some constants to a few decimal places, like pi, and c, and g, etc.). Where are you in your schooling right now?

4. Sep 1, 2015

### APAlex

Dude I'm in college that's why I'm freaking out

5. Sep 1, 2015

### APAlex

Is there anywhere I can look at all the conversions or such so I can memorize this

6. Sep 1, 2015

### Bystander

Got a CRC Hndbk?

7. Sep 1, 2015

### Staff: Mentor

Maybe wikipedia has a page on unit conversions... But just memorize the ones you will be using. It's a lot easier to memorize stuff that you use over and over...

8. Sep 1, 2015

### APAlex

Thanks guys I'm gonna go cry myself in a corner while I read these conversions over and over

9. Sep 1, 2015

### Staff: Mentor

Yoiks, I just looked at the wikipedia page, and it definitely has *Way* too many units to go through. Did you know "bucket" is an official unit of volume...?

10. Sep 1, 2015

### Staff: Mentor

And then there are furlongs per fortnight, and the number of electrons in a pint -- all kinds of cool conversions.

11. Sep 1, 2015

### APAlex

Guys I need you to keep my brain from spilling.

12. Sep 1, 2015

### Staff: Mentor

LOL

13. Sep 1, 2015

### GoodPost

Well, I know that feeling when the given quantity is in kilometers per hour and the result is required in feet per second! Anyway, you should work conversion problems as much as you can to get familiar with the conversions techniques.

* Hmm ... by the way you have a scientific calculator, don't you? ; )

Best regards,
G.P.

14. Sep 1, 2015

### Staff: Mentor

Just remember to use the trick to multiply by "1" for each unit conversion. Define your "1" so that you can cancel units to get to the final units you want.

For example, I want to convert 100km/hr into ft/s:

$$100\frac{km}{hr} * \frac{1hr}{3600s} * \frac{3280ft}{km} = 91\frac{ft}{s}$$

15. Sep 1, 2015

### GoodPost

Wow great here we go, I normally do conversions in two steps but this looks pretty simple and straightforward.
1 km = 1,000 m === (convert it into ft by the calculator ) 3280 !!

Thanks,

G.P.