Question

Q4. The speed of a bullet train is measured to be 312.0 mph ± 3.9 mph. What is the percent uncertainty in this measurement?
A. 1.3%
B. 1.2%
C. 1.25%
D. 0.0125%

Answer 1

To calculate the percent uncertainty, you can use the following formula:

\[
\text{Percent Uncertainty} = \left( \frac{\text{Absolute Uncertainty}}{\text{Measured Value}} \right) \times 100\%
\]

In this case:

- Measured Value = 312.0 mph
- Absolute Uncertainty = 3.9 mph

Now, plug these values into the formula:

\[
\text{Percent Uncertainty} = \left( \frac{3.9}{312.0} \right) \times 100\%
\]

Calculating the fraction:

\[
\frac{3.9}{312.0} \approx 0.0125
\]

Now convert this to a percentage:

\[
0.0125 \times 100\% = 1.25\%
\]

Therefore, the percent uncertainty in the measurement is **1.25%**.

The correct answer is **C. 1.25%**.