#### A marathon runner completes a 42.188-km course in 2 h, 30 min, and 12 s. There is an uncertainty of 25 m in the distance traveled and an uncertainty of 1 s in the elapsed time.

#### (a) Calculate the percent uncertainty in the distance.

#### (b) Calculate the uncertainty in the elapsed time.

#### (c) What is the average speed in meters per second?

#### (d) What is the uncertainty in the average speed?

## Solution:

### Part A

The percent uncertainty in the distance is

☚

### Part B

The uncertainty in time is

☚

### Part C

The average speed is

☚

### Part D

The percent uncertainty in the speed is the combination of uncertainties of distance and time.

Therefore, the uncertainty in the speed is

☚