# Homework Help: Sound intensity is measured on a logarithmic scale

1. Oct 25, 2007

### matt23

Here is the prob and i dont not know where or how to begin.

1.Jose was having a really bad day out on the bike. He should have checked the forecast. First, the wind coming out of nowhere. Must have been a steady 30 mph with gusts up to 50, head on. Then the lightning. First 1 km away, then 100 m away, then just 10 meters. Scary. Then the hail. First the size of a pea, then the size of a golf ball, then the size of a baseball!

Find a formula for the amount of force per unit area coming from wind blowing at a speed of S miles
per hour. As a result, supposing that a cyclist has an exposed area of 0:5 meter2, nd how much power
(in watts) the cyclist must put out to maintain a speed of 10 mph into a headwind of 10, 20, and 30 miles per hour.The top professional cyclists can produce up to a kilowatt of power in short bursts. What would this equate to in wind speed?

And the second prob is:
Sound intensity is measured on a logarithmic scale. Explain why this is the case. Find a gure for the sound intensity (in watts per centimeter2) for a person in close proximity to a lightning strike. Then give a formula for the sound intensity of the same strike when the person is R meters from the lighting strike. If a lightning bolt produces thunder at 130 dB at 10 meters, what is the intensity at 100 m? At 1 km? Can you explain why thunder is rarely heard at a distance more than 10 miles?

2. Oct 25, 2007

### dynamicsolo

What is the equation for the force of air drag?

What is the equation for sound intensity?