How to convert 1gcm⁻³ in to kg⁻³? ?

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.

An electric clothes dryer has a resistance of 8 ohms. it draws 30 a of current. what is the voltage, in volts, of the wall outlet that it is plugged into?

Find the magnetic field a distance r from the center of a long wire that has radius a and carries a uniform current per unit area j in the positive z direction.