How can density be used to identify a substance

it will be pushed away from the source of the electric field. a negative charge in a cloud induces a positive charge in the ground below the cloud.

explanation:

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up

cant without the picture! ?

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west