Question

john measures the mass of a 250 gram standard mass with a balance. Johns measure is 249.7 grams. What is the percent error of his balance? If he now measures a 1000 gram mass, what will the reading on the balance be?

Answer 1

The percentage error of measurement is expressed as

$\text{Percentage error = }\frac{\lvert Measured\text{ value - }True\text{ value}\rvert}{\text{True value}}\times100$

A) Given that John measures the mass of a 250 g standard mass to be 249.7 g, this implies that

$\begin{gathered} \text{Measured value = 249.7 g} \\ \text{True value = 250 g} \end{gathered}$

Thus, the percentage error is evaluated as

$\begin{gathered} \text{Percentage error =}\frac{\lvert249.7-250\rvert}{250}\times100 \\ =\frac{0.3}{250}\times100 \\ \Rightarrow\text{Percentage error =0.12\%} \end{gathered}$