Question

1. If the total amount of nitrogen from fertilizer that is washed into a river is 3.30 × 105 mg per year, and the river flows through the field at a rate of 600,000 liters per year (6.00 x 105 L/yr), what is the additional concentration of nitrogen (expressed in milligrams of nitrogen per liter) in the river from the farmer's fertilizer?

2. What is the volume of a 6.11 g aluminum block given that the density of aluminum is 2.70 g/cm3?

3. To qualify to run in the 2005 Boston Marathon, a distance of 26.2 miles, an 18-year-old woman had to have completed another marathon in 3 hours and 40 minutes or less. To qualify, what must a woman's average speed have been in miles per hour?

4. To qualify, what must a woman's average speed have been in meters per second? There are 1609 m in a mile.

Answer 1

Q1:

additional concentration of nitrogen = 3.30×10⁵mg/year ÷ 6.00×10⁵L/year = 0.550 mg/L (Answer)

Q2:

Volume = mass /density = 6.11g/2.70g/cm³ = 2.263 cm³

= 2.26 cm³ (Answer)

Q3:

Time = 3 hours 40 minutes =( 3 + 40/60 )hours = 11/3 hour

Average speed = distance / time taken = 26.2miles/(11/3 hour)

= 7.145 miles/hour

= 7.15 miles/hour (Answer)

Q4:

Average speed = 7.145miles /hour × (1609 m /1mile) × (1hour/3600 seconds)

= 3.1936 meters/second

= 3.19 meter/second (Answer)