3. A rock band playing an outdoor concert produces sound at 120 dB 5.0 m away from their single working loudspeaker. Ignore sound reflected from walls and other objects and consider sound originating directly from the speakers. a. What is the sound intensity level 35 m from the speaker? b. What is the delay between the time the sound leaves the speaker and arrives at this point on a very cold day (0 degrees Celsius)? A hot day (40 degrees Celsius)? c. How far away from the speaker should you stand to ensure the intensity does not exceed 80 dB, and what is the intensity at this location? 81dB, and what is the intensity at this location?

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.