If the phase angle between sound waves from two different point ...

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If the phase angle between sound waves from two different point sources is 180, what kind of interference will occur?
 
  A) destructive
  B) constructive
  C) either constructive or destructive

Question 2

Why do power tools with a plastic case not have a 3-prong plug but metal encased tools have (or should have) 3-prong plugs?
 
  What will be an ideal response?

[dawsa925]

Answer to Question 1

A

Answer to Question 2

The third wire (large round prong plug) connects to ground and grounds the metal case. A hot wire accidentally coming in contact with the case will blow a fuse. A plastic case is insulation and does not need to be grounded for safety.

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TYSM

[ecabral0]

Thanks for the timely response, appreciate it