Science+Chapter+18,+FORCES

Forces, such as magnetism and gravity, interact with objects, such as you and Earth, to produce motion.

I. What Forces Affect Objects on Earth Every Day? A. Forces, push or pull that causes change in motion B. Friction 1. Works against motion 2. Greater between rough surfaces than between smooth ones 3. Friction can produce heat C. Gravity 1. The attraction between you and the earth 2. Gravity causes objects to speed up, or accelerate, as they fall 3. Gravitational Force is the pulling of one obect in the UNIVERSE against another a. Strength of gravitational force depends on b. the mass of the objects and the distance between them D. Magnetic Force, the force of a magnet 1. surrounded by a magnetic field 2. like poles of a magnet repel 3. opposite poles attract

II. What Are Balanced and Unbalanced Forces? A. Balanced and Unbalanced Forces 1. Usually more than one force act on onject 2. If forces are = object doesn’t move, its balanced 3. One force greater than the other, object moves B. Net Force 1. Combination of all forces on an object is net force 2. To predict if an object will move, need to know amount of all forces 3. Forces going in one direction add onto each other C. Buoyant Force 1. An upward force like water is called buoyant force 2. Buoyant force = to weight of fluid an object displaces 3. Ships float because displaced water is heavier than ship D. Summary: An object does not change motion unless one force acting on it is stronger than another force acting on it.

III. What is Work, and How Is It Measured? A. Work defined 1. Using force to move an object 2. Equation for force work = force x distance 3. Symbol N means 4. Measure of work is in a unit called joules B. Machines and Work 1. Machines decrease amount of force need to move object 2. Simple machines change force needed, direction, or distance 3. Levers have 2 part, arm & fulcrum 4. Doorknob is a wheel –and – axle 5. A pulley changes the direction of force 6. A ramp is inclined plane C. Simple Machines Game D. Compound Machines Game 1.Compound machines are made up on 2 or more simple machines 2. Machines do NOT reduce work done 3. Machines decrease force, but increase distance E. Summary: Work is using a force to move an object. Simple machines reduce the amount of force necessary to move an object. Machines are made up of two or more simple machines. F. People in Science 1. Ephraim Fischbauch a. Found exceptions to law of gravitation pull b. Working on nanotechnology, microscopic machines 2. Patricia Cowings- Teaches astronauts to control their bodies 3. ¬¬¬¬¬¬¬¬¬¬¬¬¬¬Aeronautical engineers design engines and wings for aircraft

VOCABULARY

Force ________________________________________________________________________ Friction ______________________________________________________________________ Gravity_______________________________________________________________________Gravitational force_____________________________________________________________ Magnetic_____________________________________________________________________ Magnetic force_________________________________________________________________ Balanced forces________________________________________________________________ Unbalance forces_______________________________________________________________ Net force_____________________________________________________________________ Buoyant force_________________________________________________________________ Work________________________________________________________________________ Simple machine________________________________________________________________ Lever ________________________________________________________________________ Fulcrum _____________________________________________________________________ Wheel-and-axle ________________________________________________________________ Pulley________________________________________________________________________ Inclined plane__________________________________________________________________