14 Force & Motion Mr. Perez

Important Vocabulary Gravitation Force Balanced forces Unbalanced forces Inertia Contact force Friction Non-contact force Gravity

What is a force? A force is a push or a pull exerted by one object on another object. Forces have both a size (strength) and a direction (like velocity and acceleration). Newtons (N): strength of a force of an object Ex: One Newton is the force required to lift a quarter-pound hamburger

Contact Forces Contact forces are forces exerted only when two objects are touching each other Applied force: force put on an object by another object Friction is a force that opposes the relative motion of two objects that are in contact (Smooth surfaces have smaller friction forces than rough surfaces) Air resistance is a force exerted by air on an object moving in the air Buoyant force is the upward force exerted by a fluid that opposes the immersed weight of an object Normal force: The normal force is the support force exerted upon an object that is in contact with another stable object.

Non-contact Forces Non-contact forces are forces exerted by one object on another when the objects are NOT touching gravitational force: force that pulls objects towards each other law of universal Gravitation: force of gravity acts between all objects in the universe that have mass any 2 objects in the universe that have mass are attracted to each other Electrical force: force between 2 charged objects Magnetic force: the attraction or repulsion between magnetic poles

Gravitational Force

Videos https://www.youtube.com/watch?v=tEIhHwizrmQ https://www.youtube.com/watch?v=FOcY37oGhj8 https://www.youtube.com/watch?v=OpRQQjoggz8 https://www.youtube.com/watch?v=ljRlB6TuMOU http://studyjams.scholastic.com/studyjams/jams/science/sol ar-system/sgravity-and-inertia.htm http://studyjams.scholastic.com/studyjams/jams/science/for ces-and-motion/force-and-motion.htm https://www.youtube.com/watch?v=TFlVWf8JX4A

Mass and Weight Mass and weight are two different measurements Mass is the amount of matter in you Measured in kilograms (kg) Does not change depending where you are Weight is the strength of gravitational force that Earth exerts on you Measured in Newtons (N) We usually measure weight in pounds (lbs.) (1 lb = 4.4 N) Changes depending where you are

Videos https://www.youtube.com/watch?v=Y8- T8RouhPA

Inertia Objects resist having their motion changed Inertia is the tendency of an object to resist a change in its motion Inertia is the reason why an object at rest tends to stay at rest (Newton’s First Law of Motion) Inertia causes moving objects to move in a straight line at a constant speed The more mass an object has, the more inertia it has https://www.youtube.com/watch?v=qq1Whusk8No

Inertia

Combining Forces When more than one force acts on an object, they combine. The combination of all the forces acting on an object is called the net force When the forces on an object are in the same direction, they are added together When two forces on an object are in opposite directions, the net force equals the larger force minus the smaller force

Balanced and Unbalanced Forces When the net force on an object equals zero, the forces are balanced When the net force on object is NOT zero, the forces are unbalanced 20 N Right 20 N Left

Balanced and Unbalanced Forces Balances forces cause an object to stay where they are. Unbalanced forces causes an object to move (or stop moving) The speed of an object can change The direction an object is moving can change

Links https://www.youtube.com/watch?v=-F5nmIJOF4U

References Google Images Florida Science Grade 6, Glencoe Science & McGraw Hill Publishing