What are the tiny particles that make up elements called?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?