Forces Can Act Without Touching

Force Fields When a force acts at a distance, the area in which an object experiences a force is called a field.

Types of Non-contact Forces Gravitational Electrical Magnetic

Gravitational Force Gravity-Force of attraction between two objects due to mass. Attractive force (pulls objects together) The strength of the force is determined by the masses involved and the distance between them.

Factors that Affect Gravitational Pull Mass- Objects with greater mass have more attraction than objects with less mass. Distance- Objects far apart have a weaker attraction than objects that are close together.

Difference Between Mass and Weight Weight- Force of attraction due to gravity. Can change due to the amount of gravitational pull. An increase in gravitation pull will increase the weight on an object.

Mass- The amount of matter in an object. Will not change unless you add matter or take it away. It is not affected by gravity. http://www.youtube.com/watch?v=wumlTLUgPpE

Electrical Force Occurs when two charged objects exert a force on each other. Charge- property that leads to electromagnetic interactions. Protons- positive charge. Neutrons-no charge. Electrons-negative charge.

Factors that Affect Electric Force Charge- The type of charge will determine if the objects attract (pull) or repel (push). Unlike (opposite) charges attract. Like (same) charges repel. The amount of charge on each object affects the strength. (increase in charge=an increase in force)

Types of Charges

Factors That Affect Electric Force Cont. Distance- the distance between object effects the electric force. Increase in distance= a decrease in force Decrease in distance= an increase in force

Three Methods for Charging Objects Friction-two objects rubbed together causing a transfer of electrons between objects. Contact- a charged object and an uncharge object touch, and the charged object transfers its charge. Induction- rearranging charges within an object without touching.

Materials That Affect Flow of Charge Conductors- material that allows charges to move freely. Ex. Copper and many metals. Insulators- material in which charges can not flow freely. Ex. Glass, rubber, plastic Semiconductors- control the flow of charge Ex. Silicon

Magnetic Force Force that exerts from spinning electric charges. Can attract or repel objects made of iron, nickle, cobalt, or a mixtures of these metals. Like poles repel Opposite poles attract

Factors that affect Magnetism Distance- The greater the distance from the poles the weaker the magnetic field. The closer the distance to the poles the stronger the magnetic field.

Causes of Magnetism Type of atom- As electrons move in an atom it makes a magnetic field. When the amount of magnetic fields are the same, the object is not magnetized. When the amount of magnetic field are different, the object is magnetized.

Formation of domains- groups of atoms form tiny areas with north and south poles. When the north and south poles in the domains line up, the object makes a magnetic field.

Types of Magnets Ferromagnets- material that can be turned into a magnet. (permanent magnets) Ex. Iron, nickel and cobolt Electromagnets- electric current produces a magnetic field. Temporary Magnets- material whose domains temporarily line up after being rubbed with a magnet.

http://www.youtube.com/watch?v=QCaahqDZrAU