Calculating percent error in a lab

[wiccabean21]

calculating percent error in a lab please help!

Homework Statement

I have to calculate an experimental value for g using values from my lab. I got -45.9 as my value, and now i have to calculate the percent error

Homework Equations

a= g (m2 - m1/ m2+m1) was the equation i used

actual-calculate/calculated x 100

The Attempt at a Solution

Would I use negatives or not?

9.81- - 45.9 / - 45.9 x 100 = -121.4 %

or

9.81-45.9 / - 45.9 x 100 = 78.6 %

part b says derive the equation for a in the form a = F/m (f and m in terms of forces and messes in the atwood machine) but I have no idea what he is asking me to do

thank you!

 

[tiny-tim]

Welcome to PF!

Hi wiccabean21! Welcome to PF!

I have to calculate an experimental value for g using values from my lab. I got -45.9 as my value, and now i have to calculate the percent error

i] g = -45.9 is totally different from the correct figure …

either you've applied the equation incorrectly, or (more likely) you need to do the experiment again

ii] "error" means the likely error, not the actual error …

decide how much error there is in measuring each of your input figures (for example, maybe there's a 1% error in measuring each mass), and then add them (or combine them in some other way) to get an overall error in the output figure.