Friction & Gravity Standard Analyze the effects of friction & gravity on the speed & direction of an object.

Friction What is friction? What does friction affect? Two factors determine the amount of friction: a force that occurs when one object rubs against another object an object’s speed & direction the kinds of surfaces the force pressing the surfaces together

How Friction Affects Speed & Direction What does friction do? How does friction affect an object’s speed? How does friction affect an object’s direction? acts to resist sliding between two surfaces that are touching slows down or stops the motion of an object always acts in the direction opposite to the force causing the motion

Examples of Friction Friction slows or stops the motion of moving parts of machines. Athletic shoes with tread grooves to increase friction have better traction for starting or stopping motion than smooth- soled dress shoes.

Starting & Slowing with Friction Friction can make it difficult to… What must be applied to a nonmoving object to overcome the friction between the touching surfaces? The smoother the two surfaces are… start an object moving enough force to start it moving the less friction there is between them; therefore, the moving object won’t slow down as quickly

Reducing/Eliminating Friction How can you make objects move more easily? What are some ways to reduce friction? If friction could be removed, reduce friction between surfaces smooth the surfaces using wheels or rollers between the surfaces lubricate/oil the surfaces an object would continue to move.

Overcoming Friction The greater the force pushing the two surfaces together, As an object gets heavier, To move a heavy object, the stronger friction prevents the surfaces from moving. the force of friction between the surfaces becomes greater. a greater force must be applied to overcome the friction between the surfaces.

Gravity What Is gravity? Gravity affects what? Gravitational attraction depends on what? Gravity causes objects to be pulled where? a force that always attracts or pulls objects toward each other without direct contact or impact speed & direction of objects the mass of the two objects & the distance they are apart toward the center of Earth

How Gravity Affects Speed Gravity, like all forces… As an object falls… When air resistance is ignored… can change the speed of objects its speed will continually increase as Earth’s gravity continually pulls it downward all objects will speed up at the same rate they fall

How Gravity Affects Direction How does gravity affect an object that is thrown into the air’s speed & direction? The pull of Earth’s gravity causes the moon to do what 2 things? It goes up fast, slows down, & falls back toward Earth’s surface quickly stay in orbit & constantly change direction