Answer:
Contact forces are forces that require the actual contact (touching) of two pieces of matter. There are a variety of contact forces. A very common one is friction. Anytime that two surfaces are in contact with one another, there is friction between the two surfaces. A field force is a force that works at a distance. No touching is required. Gravity is a good example of a field force, because it works whether or not an object is touching something or touching nothing at all.
To determine the force per meter of a light bolt at the equator that carries 20 000 A and is perpendicular to the Earth's magnetic field with a magnitude of 3x10-5 T, we do this:
20000 / 3x10-5 = 666.67x10^6 N/m
The direction of the force would be to the left parallel to the equator.
<em>remember that
<u>loudness is directly proportional to the square of amplitude...
</u>so when amplitude is doubled ,,loudness increases four times..
when it is halved ,,,loudness is halved,,,</em>
