# Homework Help: Simple question about young's modulus

1. Nov 28, 2012

### lionely

I did a practical worked the gradient and calculated E, of a wooden metre rule.

What I want is a value to compare my value with, I got 5 N/m2

So 5N will bend the ruler 1m? Seems likely right?

2. Nov 28, 2012

### Simon Bridge

3. Nov 28, 2012

### lionely

On that page isn't that Mega Pascals?? I got 5Pa

4. Nov 28, 2012

### lionely

and maybe on that page those are MUCH higher maybe cause they calculated it using woods of greater thickness,length, etc.

5. Nov 28, 2012

### lionely

Ohhhh LOL i'm sorry I didn't even see what I typed
my mind was away. I didn't mean 5 newtons would bend it 1m

6. Nov 29, 2012

### Simon Bridge

Would you get a higher modulus if you used a thicker beam?
It's a material property. How is the modulus defined?

You can also look for other people who've done the same and talked about it.
It's a common enough experiment - done either by vertical deflection by weights or by Timing harmonic motion.

7. Nov 29, 2012

### lionely

I found out my value is very wrong D: I need to recheck my calculations

8. Nov 29, 2012

### lionely

I am so stupid =.= I left off a 10^-8 somewhere in my calculations.

New value which makes sense NOW is 5.10 x 10^7Pa.

9. Nov 29, 2012

### lionely

Sigh again i was wrong I did it over again I got 5,108.1 MPa

10. Nov 29, 2012

### Simon Bridge

When you have measurements on such a wide variation of scales, it is very easy to misplace lots of zeros :)

You can see from the discussion of accuracy in the article that these can get very big (as much as 56% it says) so you only need the right order of magnitude. "Conclude: Youngs modulus for a wooded meter-rule was experimentally determined to be _____GPa. This agrees to the same order of magnitude as an accepted value of _____GPa given in ref. ______."

If you did errors then you can also comment on how good the agreement was.

11. Nov 30, 2012

Thank you.