WARM UP What is the difference between mass

WARM UP • What is the difference between mass and weight?

THE CAUSE OF FORCES • A force is an action that has the ability to change motion. It is a push or pull • Forces can increase or decrease the speed of a moving object. • Forces can also change the direction in which an object is moving.

FOUR ELEMENTAL FORCES All forces in the universe come from only four basic forces.

UNIT OF FORCE • The newton (N) is a metric unit of force. • 1 newton (N) equals 4. 448 lbs. • If one pound of force equals 4. 448 newtons, then a 100 lb person weighs 444. 8 newtons

STRONG NUCLEAR FORCE • This force holds the nucleus of an atom together. • This is a very strong force but only reaches a short distance.

ELECTROMAGNETIC FORCE • The electromagnetic force acts between charged particles – protons and neutrons - and is the combination of all electrical and magnetic forces. • This force holds atoms together in molecules.

WEAK FORCE • The weak force is stronger than gravity, but it is only effective at very short distances. • Causes Radioactive Decay • Only occurs at a subatomic level

GRAVITY • The force of gravity on an object is called weight. • At Earth’s surface, gravity exerts a force of 9. 8 N on every kilogram of mass.

WEIGHT VS. MASS • Weight and mass are not the same. • Mass is measured in kilograms (kg). • Weight is a force measured in newtons (N). • Weight depends on mass and gravity.

CONTACT FORCES • Contact force. . Pushing a car up a hill or kicking a ball or pushing a desk across a room are some of the everyday examples where contact forces are at work. • Examples of contact forces are applied, gravitational, normal and frictional

APPLIED FORCE • An applied force is a force that is applied to an object by a person or another object. A person is pushing a desk across the room, is applying a force upon the object. The applied force is the force exerted on the desk by the person.

GRAVITATIONAL The force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface.

NORMAL FORCE The normal force is the support force exer ted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book.

FRICTIONAL FORCE Frictional Force refers to the force generated by two surfaces that contact and slide against each other.